Rolling over...again and again

Ruby Belle has just learned to roll over from her back to her tummy. she started doing this a week ago and hasn't stopped yet!! she LOVES it!! I think she did it about 15 times the first day she learned how! She doesn't love to roll from her tummy to her back even though she first did that over a month ago. so she rolls from her back to her tummy now, and is SO proud of herself, but then gets frustrated because she doesn't want to roll the other way and gets tired. funny thing is that as soon as I help her back to her back, she rolls right back over again! now, it's time for her to learn to get back herself! she's even been sleeping on her tummy a couple of days in the last week because i can't get her to stay on her back even in her crib! i know this is terrible, but if i roll her back to her back she eventually makes it back to her tummy in the night. so...i've had a few sleepless minutes (because i can't stay awake any longer) worrying about her, but what am i supposed to do?!