I'd like to tryout for my college baseball team as a freshman pitcher this year. Do I need to bring a bat?

I would bring a bat, even if you don't think you're going to have to hit. If you do need to hit you could always borrow someone else's bat but the coaches might think of you as unprepared or who doesn't care enough. Even as a pitcher they may want you to hit though, just in case they ever do need you to play a position for some reason.