Hi there. My 6 month old has recently started to roll from back to tummy in his cot. Unfortunately he has not yet mastered tummy to back rolling. We have already transitioned to sleep suits with no arms so he is able to move his head around at night/while asleep. Everyone we put him down to sleep recently even before he is fully asleep he will roll over onto his tummy to sleep. Is this an issue? Everywhere I read, it says to put your child on their back for sleep but he does not settle and fall asleep on his back anymore, immediately rolling over. First time parents so naturally quite anxious with this new stage in sleeping.

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 side or tummy.
This is not something that needs to be stopped. It is important to make his new environment as safe as possible.
https://rednose.org.au/article/what-do-we-do-now-that-a-baby-has-started-to-roll-over

Good that you have stopped swaddling/wrapping & moved him to his cot.
Babies need their arms free & the space of a cot to roll well.
How does he go with tummy time when awake?

Have a read of the Red Nose information (which includes the following) 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”
https://rednose.org.au/article/what-do-we-do-now-that-a-baby-has-started-to-roll-over