The mchn never seemed fussed about the lack of rolling but I never really expressed any concern either and up until recently had a useless one anyway. I always put her on her tummy and she was happy there so as she was rarely on back apart from sleeping gave her little practice to roll that way, and she doesn't the other either. At 12 month check she told me to put her on top of fit ball and hold then roll side to side front to back so that as she felt herself falling would try to correct and strengthen muscles that would help with crawling. My DD was in a brace 2 to 6 months, so lots of people blame that for her slowness to move, but lots of babies roll and crawl in a brace and the brace people said is down to personality rather than anything brace related. I know it is her personality from the way she is about everything, but if I had time again at 9 months I probably would ask for exercises or something if had another non roller because looking at way she moves she is quite a stiff baby.