My 10 week old rolled onto his belly in his sleep last night. I have started transferring him out of his swaddle to arms free and moving him into a cot instead of his bassinet. I’m extremely anxious and am wondering if there’s anything else I can do to ensure his safety as I wake constantly at night to check on him Thank you

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 his new environment as safe as possible.
https://rednose.org.au/article/what-do-we-do-now-that-a-baby-has-started-to-roll-over

As you have done, move him to his cot & cease swaddling him.
Have you seen him roll both ways yet?

Red Nose recommends - space of the cot & arms free, & firm, flat mattress to provide safe environment once rolling.
Remember, still always place him on his back for sleep.

Have you tried to gently roll him back when you see him sleeping on his tummy?

How does he go with tummy time when awake?
Increase his tummy time when awake - more frequently if he is not tolerating long periods on his tummy.
Increased tummy time when awake helps to build upper body strength to assist with rolling both ways.
Continue with nothing loose, soft or padded in his cot.