Seth Rogen is so exactly like his onscreen self that hanging out with him can feel a little like dropping into one of his movies. "Have just been advised Seth only needs 10 mins for grooming," reads one of the emails that shuttle between his publicists and the Guardian's photographer, which sounds about right. The roly-poly figure who turns up a few minutes later in jeans and T-shirt, topped off with jewfro and froggy grin, seems barely to need 10 minutes for anything. "Hey, what's going on?" he says, before settling into a sofa that looks custom-moulded to his contours. He talks in sentences that go up, up, up, up, up like a rollercoaster car, his furry eyebrows shooting up for emphasis, before beginning their long descent, down, down, down, down towards the point, or the punchline, which is invariably marked by that gurgling, Mutleyesque laugh of his: "Hurhurhurhurhurhur."

"I think I had my midlife crisis when I was 10," he says. "I was an angsty kid. I didn't know what I wanted to do. I remember being very disillusioned with life and I didn't like school." As soon as he realised you could be funny as a job, that was the job he wanted to do. Since then, his movies have grossed just shy of a billion dollars. Rogen is the most successful comic leading man of his generation, whether playing producer-director Judd Apatow's alter ego in The 40-Year-Old Virgin and Knocked Up or, with his writing partner Evan Goldberg, providing America's so-called "comedy mafia" with some of their biggest hits, including Superbad and Pineapple Express. This week he goes one better with his new movie This Is The End, which he co-wrote, co-produced, co-directed and stars in – thus beating to the punch Ryan Gosling, Matt Damon and every other pretty boy who aspires to direct.

"Someone had to, hurhurhur," he chortles, before adding, "The 50 days we spent making the movie were as much fun, probably more fun, than people probably imagine." The film features Rogen, Jay Baruchel, James Franco, Danny McBride and Jonah Hill, all playing themselves, holed up at Franco's house, getting high on weed when the apocalypse hits. It's the ultimate stoner freakout movie-cum-group-comedy roast, with each star sending up aspects of his persona. Baruchel is the not-quite-famous friend who complains jealously that Rogen has dropped him for his new Hollywood chums. Franco is the art-hoarding pseud whose basement is filled with memorabilia from his own films. Hill is the slick, Oscar-nominated Pollyanna who is later sodomised by the devil. McBride is the prick who eats everybody's food.

The studio, Sony, took some persuading of the basic idea. "The violence they were OK with, the sexual stuff. Never a note about demon dick," Rogen says. "It was all about us playing ourselves. They were afraid it would feel like an extended MTV movie award skit, or a Funny Or Die skit, and that it would just add a disingenuous texture to it. They were like, 'It'll make it less realistic', and we were like, 'It's more realistic. We're us. There's no break in reality between the world that you as the viewer are in and the world that we are in.'"

Interestingly, Rogen's character – the guilty sellout who's made too many movies and worries about his weight – was the last to come together. "In a way, I am the straightest guy in the movie," he says. "I play, like, the glue, the common thread between everyone, trying to make everyone happy." He seems to have a similar role in real life – if only because it is his and Goldberg's scripts that so often bring everyone together. "Lots of us are loners," Apatow says. "At the end of the day, we would rather be by ourselves. Seth likes being around people. He's much less needy than most of the people in the comedy business. He doesn't desperately seek approval. If you see Seth on a talkshow, he seems very comfortable. I never see him pacing frantically, worrying whether or not he's going to have a great spot on Letterman. He seems amused by the whole thing. A lot of us, if we don't do well, we think we're going to die. It's more like he gets a kick out of it. People definitely want to be around that. He's got his shit together."

Still, Apatow sometimes teases him: "I don't get why you're funny. Nothing really bad has ever happened to you." In a business populated by midnight prowlers mining bottomless pools of pain for their standup routines, Rogen is exceptional for his benign temperament. Not that his sense of humour isn't athletically obscene; but whether he's riffing about cacking his pants while watching Gladiator, or wondering why people have deodorants for their armpits but not their backsides, he exudes the gurgling contentment of a child. Onscreen, his persona is a matter of zero torque. "He can really go at you hard," Apatow says, "but underneath it, you know he's a good guy. I don't know why I must always look for pain. Even when it is not there."

‘It was all about us playing ourselves’: Danny McBride, Seth Rogen and James Franco in This Is The End, getting high as the apocalypse hits. Photograph: Allstar/Columbia

Nice guys aren't famous for getting ahead in Hollywood, I say to Rogen. "Oh, I've had to motherfuck a few people every now and then," he admits, his laughter acquiring a slight edge of unease. "It's a relationship-driven city in a lot of ways, and a relationship-driven industry, and if you're perceived as someone who's always happy, then you won't get treated as carefully as someone who might go ballistic every now and then." At 18, he fired his business manager ("He reacted as poorly as someone who's getting fired could possibly react") and in 2008 he fell out with Harvey Weinstein over the marketing of the Kevin Smith comedy Zack And Miri Make A Porno – but then "he's a well-documented psychopath. He was using some of Judd's movies to sell that movie, which was specifically bad because it threatened one of my closest relationships, and I was working with Judd at the time."

Goldberg, Rogen's writing partner of over a decade, says: "He is a big neurotic Jew. That's why shit turns out so well. I'm the one who's too mellow. If he was left to his own devices, he'd worry himself into a hole in the ground. Everybody thinks, because we make these so-called slacker comedies, all we do is sit around all day and smoke weed and jerk off and our jizz kinda pools and becomes the movie. Seth's been working his ass off since he was 13. Seth and Sacha Baron Cohen and Judd Apatow are the hardest-working people in the world. They're extremely driven."

When Jonah Hill was trying to figure out whether to take a part in Michael Bay's robot blockbuster Transformers, Rogen told him: "Make your own movie about fightin' robots. You can do that. That's on the table now." Hill turned the role down. When James Franco found himself taking the biggest flak of his career, over Flyboys and Tristan + Isolde, Rogen also gave him some advice. "I'd had my doubts about them, but I didn't have faith in what I was doing, or that my taste was good enough," Franco says. "Seth told me, 'Don't act in any movie you wouldn't ordinarily go see on your own if you weren't in it.' Of course! Of course you should work this way, but I didn't get it."

Not that Rogen has always taken his own advice. After Knocked Up and Superbad together took almost $300m in the summer of 2007, he found himself able to get almost anything green-lit. The result was The Green Hornet, an expensive superhero flick that struggled to recoup its $130m budget after a costly last-minute 3D conversion. "The Green Hornet was such a fucking nightmare when we were making it that it would have been a miracle if it turned into something that was in any way even presentable," Rogen says. Then there was The Guilt Trip, his 2012 road movie with Barbra Streisand playing his mother. "Again, the script was really great, but as we were making it, there was just a sense: this is not making us laugh really hard. And, honestly, the one thing those movies have in common is they're both PG-13. I tried for a year or two to think that I could be really funny in that universe, and I think what I've learned for now is I just can't. It's not as fun. What makes us laugh is really dirty, sick, edgy shit."

Hence his palpable relief about This Is The End, and the opportunity it offers him to get back on the right side of the joke. On its opening night in the US, it took $7.8m, and after five days it had taken $32.8m, recouping its entire budget. That first evening, Rogen, Goldberg, Baruchel and Hill went on an unannounced Hollywood cinema crawl, to see how the film was playing. It's a tradition they have whenever one of their movies opens. "We all go in a bunch of cars, and go to four or five theatres and peek in to see the people laugh," Goldberg says. "Half the fun is the first few days. That's really where it's at."

With Katherine Heigl in Knocked Up: ‘Seth had his comic persona when he was 16,' says Judd Apatow. 'He was already this gruff, kind-hearted person.’

Judd Apatow first noticed Rogen's gift for tender-hearted vulgarity while shooting the TV series Freaks And Geeks in the late 1990s. "He had his comic persona the first time I met him, when he was 16," he recalls. "He was already that guy. He had this gruff, WC Fields kind of personality, but you could tell that beneath it there was a very kind-hearted person." This nonjudgmental streak can be traced back to his parents, Mark and Sandy, both lefty social workers, who encouraged sex talk in the house and gave Rogen lifts to and from Vancouver's comedy clubs when he started doing standup aged 13. "He was raised around a lot of understanding and kindness," Apatow says. "If you meet his parents, they're very accepting of who he is. They adore him, and they like being around each other. There are very few people who want to spend a ton of time with their parents. When Seth's parents are around, he's thrilled to have them."

The only thing lacking was money. When Rogen was 16, his father lost his job and his mother quit hers; they put their house up for sale and moved to a smaller apartment. "We had enough money. I was fine, I had toys, I had clothes. We weren't living in a car or anything, I wasn't Jewel," he says, eliciting a snigger from the makeup girl preparing in the corner of the room. Rogen beams. "But I was just aware that we lived in a shittier neighbourhood than my friends and that our house wasn't nearly as big. And that I was the only guy that was supposed to be going to a different high school, because the high school I was supposed to be going to, I would have gotten my ass kicked every day."

He met Goldberg in barmitzvah classes after their schools merged. Goldberg remembers one barmitzvah in particular out of the 36 they attended that year – for their friend Julia Moranis, the model for the Emma Stone character in Superbad – when "everything clicked. As soon as we realised we weren't going to be kissing any girls that night, we started to hang out." At high school these two geeky Jewish kids with socialist families were suddenly thrust into a big scary world of towering, beautiful 17- and 18-year-olds. "We were fucked," Goldberg says, finding common cause with Rogen and a third friend, Sammy Fogell, in "this sense of being totally overwhelmed when we got to high school. I really think high school was one of these reasons we all have these tight friendships. Me and him and Fogell went through so much stuff together."

Their friendships, mishaps and furtive lusts found their way into Superbad, which they began writing in their teens. "The story was exactly the same: guys trying to buy beers for a girl, and one of the guys gets taken by cops and the other guy goes on this adventure," Rogen recalls. "What actually happened around that time, while we were writing the movie, was I was moving to LA and Evan went to college with one of our best friends in Montreal. I was left alone and they went off together. And what we didn't realise was, that's in a way what we were really writing about. It took Judd to tell us that. We were 18 years old, so we were still experiencing it. Then we wrote that into it and liked it so much we were like: we should start with that next time."

All their collaborations since have been elaborations on that bromance theme. "Besides their marriages, they are the closest relationships in each other's lives," Hill says of Rogen and Goldberg. "They work together, hang out every day." So we've had dudes missing other dudes at the end of high school (Superbad), dudes hitting the road together to escape bad drug dealers (Pineapple Express) and now dudes spooning one another during the apocalypse. The Green Hornet failed because the superhero and his assistant Kato weren't allowed to be dudes enough. "We really suffered from not being allowed to have Kato say to him, 'You can suck my fucking dick,' " Goldberg says. "We feel we are being fake when we aren't swearing much of the time. When my mom got breast cancer, she wasn't like, 'Aw shucks. Goddarn cancer.' She was like, 'This is the fucking worst.' When you take away the bad language, it degrades and dehumanises the whole thing. I think that's why people think our movies have heart, because when shit hits the fan, that's how people speak."

Their biggest argument – about a small tssking sound Rogen makes when he thinks an idea is dumb – happened when they were still in their teens. "We had a conversation where I was like, 'If you do that again, I'm going to fucking kill you,' " Goldberg says. " 'Stop making that noise.' And he's like, 'Well, OK… What do I say?' 'Just say, "That's a stupid fucking idea." ' We kind of went through each other's personalities and out the other side."

If Superbad showed they could write a movie, Pineapple Express showed they could write and produce a movie. This Is The End now demonstrates to the studios that they can write, direct, produce and star in a movie. It's an impressive beachhead to have secured. "I don't want to underplay how significant this whole deal is for us," Goldberg says. "Once you've directed something, no matter how shitty it is, they kind of let you keep doing it."

It's producing that's hard, they say, in which case the figure to keep an eye on is the $31m for which they made This Is The End. That's the stuff of sainthood in Hollywood, and a deal they will be able to repeat ad infinitum if the movie is a hit, although some critics have pounced on the title. Is it to be taken literally? Both Rogen and Goldberg are married now. In 2011, Rogen wed his long-time girlfriend, Lauren Miller, a comedy writer he met while working on Da Ali G Show in the late 1990s. Goldberg's wife worked on Bridesmaids. It's a far cry from the geeky adolescents who couldn't get a date in high school. Are they maturing? And, if so, can their audience be counted on to grow up alongside them?

"We get asked that a lot," Goldberg says, a little wearily.

"We do still engage in, like, life," Rogen says. "I drove here myself. I'm not some very insulated person who flies on private jets and gets taken everywhere by drivers." He says of marriage: "I'm sure it affects things to some degree. We don't fight that. Me and Evan are thinking of writing a movie with Judd, actually, about couples who are married and about to get married, so it's nice when something new happens. It gives you more fodder." Their forthcoming projects include a comedy about a guy who's having a baby but doesn't want to stop partying; an animated film Rogen has been trying to make for years; and The Interview, which reunites Rogen with Franco – the pair play journalists who go to interview Kim Jong-un and get mixed up in a CIA plot to assassinate him. His advice to Franco – only make the movies you want to see yourself – has finally come home.

"I honestly think we stopped doing that for a few years," Rogen says. "We got caught up in trying to make the movies we had opportunities to make. With this one and the next ones, we figured shit out a little bit more. We're back to making the craziest shit you could possibly be doing. We're not trying to settle into some safe zone. The more we make movies, the more we realise that the fun of making movies is taking the chance that we could be doing something disastrously bad."

• This Is The End is released on Friday 28 June.