DS2 was rolling at 3 1/2 weeks, so it wasn't pre-rolling age, but I started sleeping him on his tummy really early. The thing was, it was the only way he would sleep for ages and TBH I wish I'd realised that sooner. It might have saved us a lot of grief. I knew it was against the SIDS recommendations, but then I'm not sure that it's safe to have a really tired mum either, especially when driving etc. So sleep is important too. I did have an angelcare monitor though, so theoretically we would have been alerted if he stopped breathing. But you know, the risk of tummy sleeping for SIDS is minimal and partly theoretical (ie no-one really knows what causes it), so sometimes you just have to do what you have to do. HTH.