Hi, my baby is 12 weeks old and just started rolling from front to back only. Do I need to unswaddle now or wait until she shows signs of rolling back to front? Thanks

Yes, it is safer to have arms out of swaddle or to unswaddle once baby is starting to roll.
Red Nose recommends modifying any wrap/swaddle once baby is 3 months whether they are rolling or not.
If you wrap your baby, consider baby’s stage of development. Leave arms free once the startle reflex disappears around 3 months.
It is essential to discontinue wrapping as soon as baby starts showing signs that they can begin to roll, usually between 4-6 months of age but sometimes younger.
https://rednose.org.au/article/is-it-safe-to-wrap-swaddle-my-baby