My 7.5 month old is rolling confidently both ways and when we put him to sleep on his back sometimes he stays asleep on his back but recently he has been rolling and sleeping on his side or stomach. We have been turning him over to his back but he either wakes up or cries and just rolls over again to his side. Is it safe to let him sleep on his stomach or side now if he goes into that position himself after being put to sleep on his back? We are worried about the risk of SIDS if he isn’t sleeping on his back.

Red Nose recommendations are to “Always place baby on back for sleep” not baby must always sleep on their back.

Most babies will be rolling over by 4- 5 months. Some earlier, some later.
This is very normal as babies grow & become stronger.
Many babies then prefer to sleep on their side or tummy.
This is not something that needs to be stopped. It is important to make the “new” environment as safe as possible.
https://rednose.org.au/article/what-do-we-do-now-that-a-baby-has-started-to-roll-over

Always place baby on their back for sleep & keep head & face uncovered.
Once baby is able to roll well, is no longer swaddled/wrapped & is in a cot & can roll both ways, baby can be left to sleep in their own position of comfort.