I had them all in bed from the day I brought them home...rolling over on them never happened, I did a lot of research on this over the years...babies and adults have instincts to stop that (the rolling over and the suffocating) happening as a rule.
I think it's the way it should be really, best for baby and mom. Looking at the animal kingdom and looking at the way it was done historically before 'polite society' became involved in life, and in those tribes which aren't affected by 'our' society as yet, it's the rule, the instinct, and in any case, it was my instinct.