Mr. Trigano wanted the L.A. branch of Mama’s (as the staff calls it) to feel like a kitschy, but upscale rec room, complete with a colorful chalkboard ceiling covered in saturated, surreal art from the local painters Alex Becerra, Alex Ruthner and Pearl Hsiung. The lobby also features a lending library stocked with trashy — but essential — Los Angeles reads, like tell-all biographies of Elizabeth Taylor and Alfred Hitchcock. A row of coin-operated gumball machines line one white brick wall.

When I visited Mama’s on a sweltering spring night, the high-low social mix Mr. Trigano aimed for was in full effect. On the rooftop, which sits six stories above gritty Selma Avenue, blocks away from Graumann’s Chinese Theater and the Hollywood Walk of Fame, I found a group of young actresses playing foosball and drinking vodka and sodas — one had just gotten her big break as a lead on the now-cancelled MTV comedy “Sweet & Vicious” — next to a cluster of bespectacled friends settling into a mountain of cushy beanbags to watch “The Hangover Part II” projected onto a floating screen.

Rainbow-colored tables circle a large, rustic wooden bar, which specializes in Moscow Mules and features a 360-degree view of the Hollywood Hills. At the bar, I met Joey Zimara, 53, who until recently ran a business supplying Los Angeles restaurants with Jamaican spices. He told me that he visits hotel rooftops at least twice a week, rotating between Mama Shelter, the glitzy W, and the rooftop Highlight Room bar at the brand new Hollywood Dream Hotel, where celebrities like Jessica Alba and Alessandra Ambrosio can often be seen lounging in the private pool cabanas. “I like being on top of the world,” he said, gesturing out over the glowing sea of slow traffic snaking down Hollywood Boulevard. “I always sit at the bar, and you can meet people from everywhere. You never meet the same person twice.”

Because the roof features free Wi-Fi and is open to nonguests, many Angelenos come to the hotel during the day to write or take meetings en plein-air. Alissa Latow, a 21-year-old actress and Hollywood resident, said that she prefers to haul her laptop to the roof of Mama’s over neighborhood coffee shops. “I feel like I have a clear head up here,” she said. “Most people in L.A. don’t have jobs,” she said, sipping from a copper mule mug in a neon crop top. “Well, not in the 9 to 5 sense. They’re acting or writing or freelancing.” Ms. Latow added that she bounces between Mama Shelter and the Dream: “Mama’s is more laid back, though it gets busy around sunset. The Dream is where you go if you want to start partying at brunch and move into a pool party with a D.J. in the afternoon.”

Mr. Trigano said that attracting a steady stream of working locals like Ms. Latow to Mama Shelter was his goal for the space, which opened in 2015 in a building that once housed the Hotel Wilcox in the 1920s and later became a satellite Scientology Center. Like the Garden of Allah, he hopes that his hotel will feel as attractive for neighborhood denizens as it does for travelers just passing through. “When we picked Hollywood, it felt a little like Times Square in the 1980s,” he said. “We didn’t anticipate it to be so crazy popular that we have people coming in all day long. They work, they do yoga on the roof, they transition into a small dinner. A hotel is successful when locals make it their own place. We’ve hit that vibe now.”

6500 Selma Avenue; (323) 785-6666; mamashelter.com