G.M.
Hi A.,
When our son was a baby, we would just lay him on a blanket on the floor with toys around him to look at and he pretty much did it on his own. We would play with him a lot, and we also had a toy activity set that arched around him. You could also teach him by rolling him gently yourself. :-) Just keep at it and eventually he'll get the hang of it. Best wishes...G.