Some babies will "skip" certain milestones, only to return to them at a later time. Progression forward is what is most important. So I agree with your pediatrician, your baby's development sounds right on track. If he is able to pull to stand and cruise, then he does have the muscle strength to roll. I would consider his lack of rolling a preference of position, rather than a concerning delay. Until he enjoys rolling, you are correct to assume this may affect his ability to maintain a comfort position at night and cause sleep disruption. At this age, some families choose to do some sleep training to help encourage longer sleep. Other families prefer to attend to their babies until this phase passes. Which approach is better for you?