Aww, how sweet. I got ridiculously excited when ds learned to roll. He was exactly 15 weeks old. He's now 26 weeks old and still hasn't learned to roll back! maybe that's not normal! I think they're all different. Some never roll either way and just learn to crawl from sitting position so there's no one answer to your question really. Sorry can't be of more help! Very pleased for you though, soon every time you take your eyes off him for a second he'll have flipped himself on to his tummy. It seems to be ds' favourite pass time. I think he just enjoys the wail to be rescued as the next time I put him down, he does it all over again