C.K.
Hi N.,
They usually say once they are old enough to roll over on their own you don't have to worry about SIDS, so much, but when you say that you find him face-down in the mattress it is a little concerning. Is this an every day occurance? Does it seem to be getting to be a habit? Can you just keep an eye on him, without him knowing it, and maybe he will soon learn to roll back over on his own, or maybe he will just drop back off to sleep.
Do you give him tummy time when he is awake? The more tummy time he has the sooner he will learn to roll back over on his back. Most babies would rather sleep on their tummies, so it surprises me that he is waking up, and getting upset, because he wants to roll back over onto his back. Babies are so smart, once you start doing something, they don't forget, so it concerns me that you are starting a bad habit that you will then later have to break....do keep an eye on him though.
C.