Caught in the Act

Justin Timberlake Gets 'Social' at N.Y. Rooftop Bash

10/01/2010 at 04:00 PM EDT

He's getting social! After screening his new movie The Social Network in New York, Justin Timberlake headed to the Gansevoort Park Avenue, where he celebrated with a rooftop bash. Though girlfriend Jessica Biel wasn't there, the singer-actor was happy to chat with other party guests, and he spent most of his time in the Red Room. "Justin was really so low key," a guest says. Before the party, which also drew out Gabourey Sidibe and Lance Bass, Timberlake hosted a poolside dinner and hung out at Plunge Bar.