6 month old is a confident roller, from tummy to back and back to tummy, also able to push self up into sitting position and is pretty much crawling. We use a sleep bag. He has started to roll onto tummy during the settling to sleep process, he places his face to the side, do we leave him in this position or roll him onto his back? I’m concerned that the sleep suit/bag could make rolling to his back on his own more difficult. Thanks!

Most babies will be rolling over by 4- 5 months…...some earlier, some later. 
This is normal as babies grow & become stronger.                         
Many babies then prefer to sleep on their tummy or side.
This is not something that needs to be stopped. It is important to make her environment as safe as possible.

Is he in a cot now, not bassinet?
Does he have his arms out in the sleeping bag?
He needs his arms free & the space of the cot to roll safely.
As long as his arms are out, the sleeping bag should not impede his rolling.

**Always continue to place baby on back for sleep.

Red Nose has the following general information now that he is rolling.

Give baby extra tummy time to play when awake and supervised as this helps baby to develop stronger neck and upper body muscles which in turn enables them to roll back over.
Make sure that baby is on a firm and well-fitting mattress that is flat (not tilted or elevated).
Make sure that baby’s face and head remains uncovered (do not use lambswool, doonas, pillows, cot bumpers or soft toys)

**As babies grow and develop they become very active and learn to roll around the cot.
At this time, continue to put them on the back at the start of sleep time, but let them find their own position of comfort.
By this stage it is not necessary to wake during the night to turn baby over to the back position

Do not use any devices designed to keep baby in a particular sleep position.
https://rednose.org.au/article/what-do-we-do-now-that-a-baby-has-started-to-roll-over