when i try to rotobrush myself to float,then i get an error screen saying that the frame rate mismatched its making everyones voices high too the computer is speeding it up?
You have not provided any useful technical information like system specs, exact error messages, version info, details about your footage and comp and so on. Nobody can help you based on vague and generic statements.
Frame rate of your footage and the frame rate of your comp must match to use Rotobrush.
When you check interpretation on your footage what is the frame rate? When you check the composition settings what is the frame rate?