“Memphis” creators David Bryan and Joe DiPietro were Sunday’s big winners, taking home two Tonys apiece. At the Tony Gala, held in the Rockefeller Center Garden, the two scribes saw lots of “Memphis” producers they’d never met before. Then they retired to a party on the rooftop of the Empire Hotel, which broke up at 3 a.m. but continued at Bryan’s apartment. “I’m sure his neighbors weren’t too happy, but if you’re a rock star, you can do that,” said DiPietro, referring to Bryan’s Bon Jovi gig.