Matilda started rolling in her cot at 10 weeks and from then on wound up sleeping on her belly every night. The MCN told me once they start rolling, there isn't much you can do other than strap them down...and thats not always good for them either. By the time Matilda was 4 months she was rolling constantly both ways all the time and there was no way we'd get her to sleep other than lay her on her side & let her go.