Sleeping-back or front?

Hello all my LO is now 4.5 months old and can comfortably roll from his back to his tummy, but not yet back again. Unfortunately he now rolls onto his front in sleep and I am red-eyed from sleep deprivation, waking up every hour or so (he sleeps eight hours now) to turn him back onto his back as I am so worried about the risk of suffocation. I wondered if anyone else had experienced this problem with their LO and what they did. I hoped eight hours of sleep would include all of us!!! Clare (happy but tired mum to Ernie)