My 6 month old baby rolls over on his stomach but does not roll back. his face is down on his mattress, i put him back facing the ceiling, but he backs to the position on his stomach, is anything i can do to prevent this? is it dangerous?

We always want to start them on their backs until they reach a year of age, but you can't control their movements as their development progresses. After 5 months the risk of crib death is so low I don't consider getting up at night to re-position them worth the effort.

Avoid excessive bedding so that your son's nose and mouth are not obstructed. Head control improves and allows him to reposition. Back to sleep is advised, but this is common. Check on him periodically during the nigh, or consider a monitor. Please follow up with your Pediatrician