Master 6 months won’t settle on his back in his cot. We put him to sleep on his back and immediately roll onto his side. He can roll back to front (from 4 months he learnt this) and worm crawl to get around. He has only rolled independently from his front to back a few times (that we’ve seen). He can lift his head/body to the point he is constantly up on his hands and feet trying to be on the move. No mater how long he has been asleep, as soon as you roll him he will wake up and roll back.m. I am unsure what to do. Any help would be greatly appreciated.

Most babies will be rolling over by 4- 5 months. This is very normal as babies grow & become stronger.
Many babies then prefer to sleep on their tummy.
This is not something that needs to be stopped. It is important to make his new environment as safe as possible.

Ensure that the cot mattress is firm & flat & there is nothing soft or loose in his cot.
Always continue to place baby on back to sleep.
Increasing tummy time when awake may also helpful.
I assume his arms are free in the sleep bag you are using -  he needs his arms free.

Red Nose has the following information now that your baby is starting to roll.

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