My daughter is 8 months old and has recently started rolling onto her stomach to sleep, can I allow her to do this at this age or should I keep moving her onto her back. And if not, at what age can a baby/child safely sleep on there stomach

What you describe is a normal phase of development. Most babies will be rolling by 4-6 months of age.
It is important now, that your baby is in her cot for all sleeps - she needs that space to roll safely.
Also ensure that mattress is firm & well-fitting & that there is nothing loose, soft or padded in the cot.
Wrapping should be ceased, if you haven’t already.

Always place her on the back for sleep.

Red Nose has the following information:
As babies grow and develop they become very active and learn to roll around in the cot.

At this time, continue to put them on the back at the start of sleep time, but let them find their own natural sleeping position. 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. These can be dangerous and they are not recommended.
https://rednose.org.au/article/what-do-we-do-now-that-a-baby-has-started-to-roll-over