My LO will be four months on 11/23 and she recently started rolling from back to belly so we stopped swaddling her and are using a Halo transition swaddle where her arms are free. She's not sleeping through the night anymore, which we expected while she got used to not being swaddled but last night my husband woke me up to show me that she had rolled over and fallen asleep face down. Now I'm in a panic about her rolling onto her face at night when I'm sleeping but I'm not sure what I can even do about it! She isn't able to roll from belly to back yet, btw...
Re: Rolling onto belly at night and I'm scared.
You could get a Snuza monitor, I also saw one recently that's like a little sock and monitors breathing.
Of more interest is the breathable crib mattress. Basically it fits over a box-like piece and it's breathable, so even if baby is face-down on it it's open on the underside so they can breathe. I saw it as an ad on Facebook and can't remember the name of it! Maybe someone else does. I was thinking of getting one myself.
ETA: found it. Secure Beginnings: https://www.securebeginnings.com