Went through this with my two and the second one was easier because I put two towels rolled up under one of those thick crib blankets so that he felt swaddled. I know you are not supposed to put anything in the crib so I was reluctant. But I put the blankets rolled up like tubes and put them so they'd be under each side of him and used one of those stiffer decorative square crib blankets. Did this for a couple days, then removed one towel then the other so by the time he was anywhere near rolling over, the towels were gone. Worked very well.
Updated
Went through this with my two and the second one was easier because I put two towels rolled up under one of those thick crib blankets so that he felt swaddled. I know you are not supposed to put anything in the crib so I was reluctant. But I put the blankets rolled up like tubes and put them so they'd be under each side of him and used one of those stiffer decorative square crib blankets. Did this for a couple days, then removed one towel then the other so by the time he was anywhere near rolling over, the towels were gone. Worked very well.
Updated
Went through this with my two and the second one was easier because I put two towels rolled up under one of those thick crib blankets so that he felt swaddled. I know you are not supposed to put anything in the crib so I was reluctant. But I put the blankets rolled up like tubes and put them so they'd be under each side of him and used one of those stiffer decorative square crib blankets. Did this for a couple days, then removed one towel then the other so by the time he was anywhere near rolling over, the towels were gone. Worked very well.