Freaking out here

My daughter is almost 4 months old and within the past couple weeks she has master rolling over from back to tummy. We’ve switched from a swaddle to a Zipadee-zip for sleeping and thankfully that transition was seamless. But she rolls a lot in her sleep. When I look over at the baby monitor, I usually find her sleeping on her side. Now, two days in a row and twice this morning I found her sleeping on her stomach, and one of those times her face was totally down. Thankfully the mattress was firm enough that her nostrils were not covered. Anyone else have experience with this? Is there anything I can do?