Just wondering when wearing mittens for sleep should stop? Nearly 5mo rolling both ways, however does a lot of face rubbing with his hands and I’m concerned he’ll constantly have a scratched face, but also wondering if it’s restricting the use of his hands when he’s on his tummy

There is no specific answer to this question.

Does he scratch his face when he is rubbing it?
It is not uncommon for babies to want to touch their face or suck on fingers as part of soothing or settling.
Some mittens may be made of material where baby could suck off some of the material.

Not sure if the use of mittens would restrict his ability to roll - as you said he’s rolling well & both ways.