To alternate turns at a one player video game, such as tetris, or asteriods. The phrase is a reference to the act of passing the controller, or "rock" between people.
"Pass the Rock" meaning pass the ball but using another word for the ball. There is a ball brand called the Rock and people commonly say this when they want you to pass the ball to them.
12 step recovery jargon referring to someone new who talks about how great life is, now that they'resober. Usually meaning that the person is out of touch with reality.
The new guy seems pretty happy for a dude who has no job, no money and no family. He must be on a pink cloud.