She sits..but doesn't roll

Emiline has yet to roll over. She is now about 41/2 months. At first I thought it was because she never spent time on the floor. She is either being held (yeah, she's spoiled!) or in her swing or carseat for safety reasons (lots of action in our house). So the last month, I've given her a lot more floor time. She still doesn't roll. She'll lean over on her side, but then look at you and fall back on her back or tummy. Funny girl. I'm not worried at all about her developmentally, because she is starting to sit up (Madison counted up to 26 the other day). She's just going to be stubborn. At least she'll be able to hold her own in this crazy family of ours!!