The made-in-Michigan rock musician introduced Ryan during a rally Monday night in the Detroit suburb of Rochester.
The rapper, born Robert Ritchie, told the raucous crowd gathered at Oakland University that he believes "you have to stand for something" even if it may alienate a few fans.
Rock added that it was OK to disagree, particularly in a music business that he says "leans very left."
He quieted the crowd a bit when he shared his pride over the election of Barack Obama as the first black president. But he quickly added he was sorry Obama "didn't do a better job."