Rolling Over

We're behind the times. Rolling over should have been a thing months ago but Libby has decided to make it her new favorite thing to do in her crib. Jim and I keep finding her flat on her stomach in the corner of her crib with a huge grin or sad face pretty much constantly now. I've never actually witnessed her rolling from her back to her tummy but she can obviously do it unless Max the Cat is assisting her in some way. Now the problem is, do I worry about her sleeping with her being on her tummy? She seems to prefer it since she's always moving that direction...but I cannot help but worry about her not being able to breathe. When does the worrying stop? Oh, never? Right. =)