Nostalgia dominated the Feb. 15 “Rock of Ages” opening at the Pantages theater, not just for 1980s anthems like “Don’t Stop Believin’” but also for memories of five years ago when the stage show debuted a few blocks away at King King and then moved to the Vanguard.“We didn’t know what we were doing but we had a lot of passion for the idea of celebrating the music,” noted producer Matt Weaver at the Spot 5750 after-party. “We had to strike the set by 10:30 every night so they could have raves, and I remember there were all these kids with glow sticks waiting to get in. Who would have thought when we were starting this that we’d wind up with a movie with Tom Cruise?” Fellow producer Janet Rich allowed that taking the tuner back to L.A. after five years represented a vindication with Broadway cast members and rockers such as REO Speedwagon’s Kevin Cronin in attendance. “I’m so glad we’re here since it’s a love letter to the Sunset Strip and what’s great about LA,” she added. Constantine Maroulis, who’s been the lead for last three years, admitted that he had butterflies before hitting the stage. “I really did feel a lot more pressure since it’s a big deal for us to come back to Los Angeles.” The after-party featured music videos of such standards as “Rock and Roll All Night,” “Can’t Drive 55,” “Love and Affection” and “Cold as Ice,” along with Weaver warbling “Eye of the Tiger.” “If we didn’t have the music, we wouldn’t have anything,” he said.