If you want to be "spoiled," this is from the scene in the movie which got posted yesterday. It also confirms that Zac is indeed playing Dan Janjigian who played the drug dealer, Chris-R, in The Room.
From an interview with Rob Lowe's co-star Hana Hayes with Instyle:
“I’ve loved Zac Efron ever since he played Troy Bolton in High School Musical,” said Hayes. “One day he Tweeted about The Grinder, and I asked Rob if he had seen the Tweet. He said, ‘Little Zacky? He’s basically lived at my house before!’ Then we started talking about whether or not he’s too old for me to date, but Rob said, ‘He’d have to get through me first.’ We’re like a very loving family, which is nice.”