"I'm not going to be the vice president," Ruhbio, R-Fla. and tea party favorite said at the opening of a new constituent office in Palm Beach Gardens.
Asked about a suggestion by former Florida Gov. Jeb Bush that he is the clear choice as Romney's running mate, Rubio returned the favor, saying: "I think Jeb would be a great VP."
Rubio has endorsed Romney and declared the primary over even though "everybody may not agree with who's won."
The first-term senator also predicted a victory for opponents of President Barack Obama's signature health care legislation, saying "I'm fairly confident that the Supreme Court is going to render a decision that's true to the Constitution, which in my opinion means they're going to overturn significant portions of the health care law."
Rubio also weighed in on the case of Trayvon Martin, the 17-year-old whose Feb. 26 shooting death at the hands of a neighborhood watch volunteer has spurred debate over Florida's "stand your ground" law that allows for the use of deadly force during a confrontation.
Rubio supported the law while in the state House and says it's premature to talk about repealing it.
"I don't know what happened in this case, but `stand your ground' does not allow you to chase somebody and shoot them," he said. "So I'm not saying that's what happened in this case, but if it happened in this case or in any other case, `stand your ground' doesn't apply."
Rubio called the shooting "a tremendous tragedy" but said he was "troubled people are rushing to judgment."