Rhodes, a junior, said he has been projected as a late-first-round or early-second-round pick.
"I'm gone," Rhodes told ESPN on Tuesday. "I did all I could in college. If I was to come back, I don't think my status would be getting any better."
Thompson, who sustained season-ending injuries the last two seasons, told The Orlando Sentinel he would also head to the draft instead of trying to get a sixth year at Florida State.
Defensive end Brandon Jenkins has already declared himself eligible for the draft. Two more players -- defensive end Bjoern Werner and safety Lamarcus Joyner, said after the Orange Bowl game Tuesday they would take a few days before announcing whether they, too, would leave school for the NFL draft.