Baby rolling on stomach

My girl is about 3 1/2 months old and has started rolling from her back to her stomach a lot. But can’t roll from stomach to back yet. The last couple nights she will not stop rolling on her stomach to sleep. It’s making me really nervous, sometimes she even rolls and has her face pushed into the mattress. I’m nervous she is going to suffocate while I’m sleeping. There is nothing in the crib, just a fitted sheet. But she can still suffocate if her face is pushed into the mattress right? Do I need to try to keep her rolled on her back? How do I do that? Please help me, I need to sleep and I can’t when I’m scared to take my eyes off her 😔