3.5 month old baby has started rolling into side, we have always used an ergo sleep bag (arms in) and a bubba blue tuck sheet Now her arms are out and tuck sheet removed we have had a hard time putting her back down after nightly feeds as she lifts her legs and flails her arms restlessly Is it ok to still use bubba blue tuck sheet to help keep her lower body secured to prevent restlessness, If not should she grow out of pulling her legs up and walking them back down? Thankyou

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 her new environment as safe as possible.
https://rednose.org.au/article/what-do-we-do-now-that-a-baby-has-started-to-roll-over

I think it would be safest to also transfer er to her cot now, if not already there.
It is important to be unswaddled now (arms free)
Red Nose recommends - space of the cot & arms free, & firm, flat mattress to provide safe environment once rolling.
Remember, still always place her on her back for sleep.

Baby will wriggle, squirm & move around in varying degrees for all sorts of reasons - many like arms free to touch their face &/or suck fingers. Many others like to kick their legs. This is all very normal.

How does she go with tummy time when awake?
Increased tummy time when awake helps to build upper body strength to assist with rolling both ways.
Continue with nothing loose, soft or padded in her cot.

Often, once baby is rolling & kicking legs in the cot, it is preferable to not use bedding/covers especially if it makes rolling more difficult.
If she is not restricted (moving) by the bedding then it could still be used for now, but if she is attempting to get out of the bedding it may be time to stop using.
Babies are all different, so it can be difficult to be specific with some guidance.