Law Roach swipes the key card to his penthouse suite and a little red light signals no entry. When the same thing happens again, he sinks slowly to the floor, phoning his assistant to inform her, wearily, “Wrong key. It’s the wrong key.” It’s been a long New York fashion week, and Roach, the most hyped celebrity stylist working in the US today, is tired.

This week, Roach has been dressing comedian and actor Tiffany Haddish, and it’s been the usual merry-go-round of shows, including his first catwalk styling gig, for Chinese brand Bosideng. An interesting one, because “the designer spoke no English and I spoke no Mandarin”, Roach tells me. “But the language of fashion is so strong, during fittings we would just look at each other with a ‘yes’ or a ‘no’.”

Then there have been the parties, culminating in Rihanna’s Diamond Ball, to which he wore Schiaparelli couture. Declaring himself a lover of vintage and “thrifty” clothes, Roach today sports a more low-key look: a black polyester tracksuit with 1970s-style flared pants, a pair of beat-up Converse hi-tops and a quilted leather cap by Chanel. He often wears an elaborate hair weave, but today his head is shorn smooth.

Finally, the correct key arrives. Inside the suite, it looks like a fashion week bomb has gone off. Settling on a sofa amid racks of clothes, half-eaten sandwiches and garment bags exploding with sequins and stilettos, Roach exudes the nonchalant cool of somebody who could make a bin bag look chic. “I think fashion and style are two totally different things,” he says. “You can’t teach style. You either have it or you don’t. It has nothing to do with access. It has nothing to do with labels.”

Céline Dion in Giambattista Valli dress. Photograph: Getty Images

Known as @luxurylaw to his 370,000 Instagram followers, Roach is now a TV star in his own right, having just filmed his second series as a judge on America’s Next Top Model. He is the man responsible for Céline Dion’s 2016 transformation, practically overnight, from midlife chanteuse to fashion maven, and for catapulting breakout Disney star Zendaya into the spotlight. In May, he made number 12 in the Hollywood Reporter’s Most Powerful Stylists list, an accolade that, according to his agency, makes him “the biggest African American stylist in the game”.

Considering the term stylist to be “overused”, however, Roach prefers to think of himself as an “image architect”. It’s a term that reflects the shifting role of celebrity dressers in 2018, where one killer look going viral on social media can lead to overnight fame (with the lucrative contracts to match), and campaigns such as Time’s Up have turned the red carpet into a political platform. “What I do is similar to what an architect does,” Roach explains. “The surveying, building a blueprint, sourcing materials, all that. But I’m doing it with clothes, jewellery, hair and makeup.”

It’s all a long way from his humble roots growing up in Chicago, the eldest of five children. “It was really, really tough,” he says. “I didn’t have the most stable family dynamic, so I figured out early on that I had to make my own way.” Fashion, as paraded on reruns of Dynasty and Charlie’s Angels, was his escape. As for any ambitions about working in the industry, “I never really thought that, because I didn’t know there was an industry.”

It was his grandmother Eloise who introduced him to vintage shopping, or what she called “junking”. “I would go through the women’s racks out of curiosity and buy a few things here and there.” As Roach’s collection grew, he stashed the clothes in the boot of his car (“my mother thought it was weird and hated the smell”). Before long, he was loaning things to his most stylish girlfriends, and when they began fighting over pieces at makeshift boot sales, “I was like, ‘Oh shit, this is a business.’”

Zendaya rocks a mullet. Photograph: FilmMagic

There followed a bricks-and-mortar store, Deliciously Vintage, and eventually personal clients. One moved to LA and flew Roach out for a shopping session, where a serendipitous meeting led to his break into the world of red-carpet dressing. “The day I arrived, a beautiful girl came by with her dad, and it was Zendaya,” he says. She was 14 at the time; Roach ended up taking her shopping for an outfit for Justin Bieber’s Never Say Never premiere. The resulting look was “a puke-green, patent-leather Alexander Wang skirt with a silver Alice and Olivia blazer. We were like, ‘People are either gonna love it or hate it, but we love it.’” The pair have worked together ever since.

At the start, Roach had a tactic for getting Zendaya noticed. “Nobody wanted to dress her when she wasn’t known, so I would put her in things that other people had already worn.” This earned her exposure in the celebrity weeklies’ Who Wore It Better columns and, soon enough, “people started to know her name”.

‘When a client gets dressed, there’s this new persona she takes on.’ Photograph: Caroll Taveras/The Guardian

How does he feel about being an industry name? “It’s flattering,” he says, “but I do what I do because I love women, and playing a part in making them feel beautiful. When a client gets dressed, there’s this new walk, this new persona that she takes on. When I see that, it drives me crazy. It’s like my drug.”

When it comes to his own celebrity, he says, “It’s more important that people who look like me and who come from where I come from get to see that this is possible.” As well as being the highest-ranking African American, he was one of only five black people to be recognised on the Hollywood Reporter’s stylists list, all of them male. “It’s the same [white] women on the list every year. And all the new people are the assistants of those women. You get into this industry from interning, and you have to be financially stable to intern for two, three, four years. If you don’t come from a family that allows you to do that, then how do you do it?”

Céline Dion in Vetements’ Titanic sweatshirt. Photograph: FameFlynet

That the fashion industry is elitist and blindingly white is nothing new, and yet, against a backdrop of 2018’s call-out culture, designers, retailers and agencies alike are being asked to shake up the status quo – or face dying out. In August this year, New York Magazine’s blog The Cut ran an extended editorial titled What It’s Really Like To Be Black And Work In Fashion, in which more than 100 people were interviewed about their experiences in a culture where tokenism is alive and thriving. Among the Council of Fashion Designers of America, only 15 of its 500 members are black. When Tyler Mitchell shot Beyoncé for the September 2018 cover of US Vogue, it was a first for a black photographer in the magazine’s 126-year history.

Roach argues that there needs to be diversity behind the scenes as well as on the red carpet. “If you’re fighting for inclusion, it has to trickle all the way down to the hair and makeup, to the cameramen and the sound engineers. People say, ‘Isn’t it getting better, though?’ To which I reply, ‘Oh yeah, it’s getting better for me. But what about everybody else who looks like me? I can’t be in this industry and be the only one. I can’t do that.’”

What Roach can do is craft pop-culture moments that position his clients at the centre of the zeitgeist, such as the time he sent Zendaya down the 2015 Oscars red carpet in cream silk Vivienne Westwood, set off by a full head of dreadlocks. Comments from TV presenter Giuliana Rancic that they made the then 19-year-old look like she “smells like patchouli oil. Or weed” led to a public outcry, and a statement on Instagram from Zendaya denouncing a stereotype that was “outrageously offensive”.

For his part, Roach is proud to have played a part in sparking a conversation about “what’s appropriate for black hair at the Oscars. What’s appropriate for black hair in the workplace. That story got billions of impressions, and I believe it did help to bring about change.”

He constructed a less political “statement look” for Céline Dion at the 2017 Billboard Awards, dressing her in an angel-winged gown by Stéphane Rolland Haute Couture. Roach says that when it was first suggested they meet, back in 2016, “I was so excited, I couldn’t sleep.” After a 45-minute meeting in Vegas, Dion asked him to travel to Paris with her for a month to take care of her street-style wardrobe, before hiring him to oversee her stage looks.

When she stepped out in an outsized Vetements Titanic sweatshirt (the hoodie a genius reference to the film soundtracked by her classic tear-jerker My Heart Will Go On), fashionista.com declared Dion the “queen of the world”. Roach hadn’t been sure Dion would go for it, but remembers her reaction as being: “‘What do you mean, what do I think about it? I love it. I want to wear it today.’” Roach styled the sweatshirt with blue jeans and a pair of gold Gucci heels, to the delight of the press pack.

Zendaya’s Oscars look in 2015. Photograph: WireImage

With a client list that also includes Anne Hathaway and Ariana Grande, what do the people he dresses have in common? “You want to play, and you want to take risks. My clients also don’t care what people say,” he says, offering another Zendaya red-carpet moment as a case in point. “We went to the Grammys after David Bowie had just passed, and she wore a tuxedo and a mullet in homage. You’ve got to be a strong girl to do that on the red carpet. You have to have conviction to say, ‘I like this, and I think I look cool, and fuck you to everybody who doesn’t.’ I think all my girls have an element of ‘fuck you’ in them.”

This is something of a mantra for Roach: he even has the phrase tattooed on the middle finger of his right hand. As for dream jobs, “the people I would have loved to work with are no longer with us. Prince, Amy Winehouse. I always felt connected to Amy, in a way.”

If success for Roach is in the work itself, then landing the America’s Next Top Model gig is a marker of how far he’s come from his days junking back home in Chicago – in particular, filming his second series with the show’s creator and executive producer Tyra Banks, one of only a handful of African American supermodels, after she returned as a host this year. “When we were shooting our cast photo, I’m there with Tyra, in front of the ANTM logo, and I start to cry. I was like, ‘We’re in the house that Tyra built!’”

It’s another opportunity for him to increase the visibility of black creatives in the industry. He shows me his tattoos, the affirmation “I can, I will” and the number “312” (his Chicago area code) – reminders that “I am a lot of firsts for my family. The first to graduate high school. The first to earn a college degree. The first to move out of Chicago. If I can inspire somebody else to be a first, that’s what’s important.”

Who dresses who: meet the other power stylists

Karla Welch

The Canadian’s client list includes Lorde, Amy Poehler, Amandla Stenberg, Elisabeth Moss and Katy Perry as well as, more surprisingly, Justin Bieber.

Although her personal style is low-key (she has described herself as a “Celine woman”, of the Phoebe Philo mould) it is the big fashion-career-shaping “moments” which Welch is most known for. She has been credited with catapulting Ruth Negga to best-dressed status via some custom-made Louis Vuitton.

Donald Glover in Gucci suit. Photograph: Getty Images for Vanity Fair

Ilaria Urbinati

One of Hollywood’s top men’s stylist, Urbinati has dressed Armie Hammer in Gucci tuxes, Sacha Baron Cohen in Paul Smith suits, and Rami Malek in Givenchy leather jackets. Other big-name clients include Bradley Cooper, Dwayne “The Rock” Johnson and Tom Hiddleston.

But she is perhaps best known for her recent work with Donald Glover, dressing him in Gucci suits, from brown velvet to thick pinstripe. Urbinati is big on what she calls “aggressive styling” – bold colours, prints (see The Rock in a Hawaiian shirt) and jewellery.

Leith Clark

This London-based, Canadian stylist’s name has become a byword for the romantic look – think Keira Knightly in floaty Chanel couture or Erdem dresses; florals, lace and long hemlines.

Clark (a former housemate of Alexa Chung) most recently worked with Batsheva, fashion’s favourite new dress brand (known for remixed prairie dresses inspired by Orthodox Judaism). She is also the founder-editor of Violet, a fashion magazine that aims to represent diverse women of all ages.

Marni Senofonte

Most famous for shaping the Beyoncé Lemonade album look (and that iconic pregnancy shoot), Senofonte works with musicians from Lauryn Hill to Diddy. She is branching out, recently taking on Kendall Jenner as a client (her sister Kim Kardashian is an old friend).

Senofonte’s aesthetic is high-octane and attention-wielding – think Beyoncé’s Michael Jackson-inspired leather military jacket with fishnets for the Black Panther Super Bowl performance, or the unmissable yellow Cavalli dress she wore for the Hold Up video. Ellie Violet Bramley

• This article was amended on 8 October 2018 to remove a reference to the model Ruby Rose, who is not currently a Law Roach client

