Our 3 month old has started to roll front to back during tummy time (but can’t roll back ~ front) would you recommend to transition from arms in to an arms out sleep sack? I noticed the Love to Dream transition bags are not suitable for her weight (she is 5kg) as they start from 6kg onwards. What would your recommendation be currently?

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  (please read full article)

Recommendation would be to have baby with arms out (cease swaddling) & move to a cot as she is “attempting to roll” - baby needs arms free & space of a cot to roll well & safely. (see article linked above)

How does she go with tummy time when awake.
Increase tummy time when awake, as this will help to build upper body strength & roll well & confidently.
Is she rolling to her tummy at all or for sleep?
How have you been managing that?