Hello, my almost six month old is put on her back to sleep, she was initially moving to her side to sleep but lately she has decided to sleep face down with her hands tucked under her eye area. Her head isn’t to one side it’s face down on the mattress and it’s terrifying: I roll her back but she does it constantly all night, am I better trying to move her head to one side? Im exhausted checking her hourly and im sure the constantly hourly rolling is tiring her too. During the day she rolls stomach to back both ways, not as strong stomach to back Thanks

Red Nose recommendations are to “always place baby on back for sleep”  NOT baby must always sleep on their back.
https://rednose.org.au/article/red-nose-safe-sleeping-recommendations

Most babies will be rolling over by 4- 5 months. Some earlier, some later.
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 the “new” environment as safe as possible.
https://rednose.org.au/article/what-do-we-do-now-that-a-baby-has-started-to-roll-over 

Have you ceased swaddling her?
Babies need arms free & the space of a cot to roll well.
Ensure mattress is firm & flat & nothing soft or loose in her cot.
Continue to always place your baby on back for sleep.

You could gently turn her face to the side if you see her face planted.
Parents are not expected to sit up all night watching their baby.
As she is able to roll both ways, still place her on his back, but let her find her own position of comfort.  (see linked article above)