Mason had his first 'roll-over' from tummy to back on his 4 month 'birth day' but I kinda thought it may have been a fluke because he was on the futon and it wasn't exactly flat.? But when I put him on the floor at my parents house, he definately rolls over! I've noticed he has a bit of trouble rolling if he has his overalls on and it's better if he only has a onesie on, less bulk?