Will the fact that my feet are over pronated(roll inward) cause problems in ballet? if so, how can I fix it?

I don't think that it would effect anything like that, but it might look bad while you're dancing, especially if you roll in on plie or in positions such as first and fifth. If you go see a foot doctor, they can prescribe insoles that will prevent your feet from rolling in. My friend, who (like me) is serious about dance, has the same problem. She got insoles and I have tried on her shoes... ah they are so comfortable and they will help. If you don't get those (or until) just focus on keeping all of your toes flat on the floor and make sure your not trying to turn out from your knees as this can make it worse. Always always always turn out from your hips and hip flexers. (: