My DD rolls her wrists over when she swings. With any luck sometime today i can get some video of her swing, I'm sure that will help you with advice. I am looking for drills and tips to help her stop this. Thanks.
When you get the video, make certain that we can see her grip on the bat. If the bat is too far back in the hand, as opposed to being out on the fingers, it can contribute to rolling the hands.
Easton Turbo Slot gloves are good to use, to combat this - as well as the videos posted by Hitter and Crystl Bustos.