K.S.
Don't worry, my son rolled over around that age and then stopped doing it for about 6 months. He also hated tummy time and so we used a great technique I learned from the ECFE person at the hospital. Get a beach ball, blow it up so it is round but deflated somewhat. Then place the child on his tummy on it and roll it back and forth gently while hanging onto to him enough to keep him from falling off. He will use all sorts of his neck, back, and torso muscles. It is also great for getting rid of gas in tummies.