Rolling onto stomach when sleeping

Ja

My 4 month old keeps rolling onto her stomach while she’s sleeping ever since she discovered she can do that now. She looks so comfy, and I keep rolling her back onto her back, but she fusses and eventually rolls back over. I googled it, and the two different opinions I got said it’s safe to let her do it if she’s able to roll on her own, or to roll her back every time she does it. Which one is right?