Rolling over!!!!

My 3 month old just rolled over from his back to his tummy for the first time ever & it was while he was asleep. He uses a sleep sack. Arms are out (not swaddled) still doesn’t really know how to roll back over, been trying to teach him bc he only knew how to roll tummy to back just recently…

Do I keep him in sleep sack? Tips? We have mini crib that he’s still good size for…

My anxiety is crazy