Once they can roll over consistently from back to tummy, then there is not much you can do but it means they are strong enough to get their head to the side to breathe. Usually babies can roll from tummy to back long before they roll from back to tummy, so they should be able to roll back to their back. I do believe though once the baby can roll from back to tummy and you are swaddling them, that you need to stop swaddling them since they need to be able to have use of their arms to get themselves into a better position if they rolled over awkwardly. This includes any swaddle sacks you use. We are using the Woombie (one brand of swaddle sack) and I know as soon as she shows she can roll from back to front, that we will have to transition to the arms out woombie and/or sleep sacks with arms out and free.
You still want to keep the crib clear of toys, blankets and bumpers - suffocation risks are still present if they roll and trap themselves (especially with bumpers) and can not free themselves when their air is cut off. This is why even those mesh things to keep the babies from climbing out makes me cringe - they have the same risks.
Note - in that same vein - if you did not see that major recall of the peapod travel bed for infants, please be sure to follow up on that if you own one. We got one but never used it for some reason, and after that recall, we plan to junk it since it makes us way too nervous even with their repair kit to trust it won't be a safety hazard.