An Oscar-winning actress in Rocky Horror? Well, not for RHPS (a VERY early film), but Susan Sarandon did go on later to be nominated for an Oscar for Atlantic City,
Thelma & Louise, Lorenzo's Oil, and The Client, and won for best actress in Dead Man Walking.
Some trivia: She is a UNICEF goodwill ambassador... Was chosen by People Magazine (1996) as one of the 50 most beautiful people... Keeps her Oscar in the bathroom.