I believe my child has the mental knowledge necessary to roll over. My child can do a mini-pushup where head and chest are lifted and the upper body is supported by the forearms. She also "swims" her legs when placed on her tummy. My child also has the instinct to move to get a toy. If I place a toy in front of her and just out of reach, then provide resistance on her feet she will scootch/army crawl (with my help) to get the toy.
However if I place a toy out of reach to one side as is suggested to encourage rolling from tummy to back, my child simply ignores it. Instead of rolling she eventually fusses to be either picked up or placed on her back again where she can see the world more easily. Besides waiting until she does it on her own, is there anything I can do to encourage her to roll? We provide tummy time at least once during all awake times, adding up to at least the minimum recommended 20 minutes daily.