Stop swaddling your baby when they can roll over while swaddled. The reason is that the risk of SIDs is increased if babies can roll from the their back to their front while their arms are still contained. In general, when babies sleep on their stomach, the risk of SIDs is increased. So, it is better for them to sleep on their back, though we can’t control their position once they start rolling over. Once babies can roll to their stomach, it is better if they have free arms. Having more arm control must somehow reduce the risk of SIDs.
If you are concerned about how your baby will sleep once you can no longer swaddle them, no worries! You can still use a transitional swaddle. Transitional swaddles allow arm movement but help with baby jerk reflexes that are thought to wake them up. Unfortunately, I don’t have specific data on the efficacy of transitional swaddles but I used them for both of my kids, and they had no issues waking up at night once we stopped swaddling. (I can’t rule out that perhaps they just no longer needed swaddling but my kids rolled over quite early, so they possibly did.) We used the Baby Merlin transitional swaddle and thought it worked great. Here is a link and picture of my son in a Baby Merlin. Even if not absolutely necessary, it works as a sleep sack/blanket as well. My kids seemed to like the coziness.
Swaddling really does help babies sleep better: https://think-parent.com/baby-sleep-hack-how-swaddling-works-according-to-science/. The exact age at which babies no longer need to be swaddled for improved sleep is probably around six months or earlier, definitely by nine months old. The jerk reflex (Moro reflex) that is thought to wake them up is usually gone by six months or sooner. We stopped using a transitional swaddle around nine months old and had no issues with our kids waking up.
Does your baby break out of their swaddle? Try a swaddle strap! Traditional swaddling or swaddle sacks (such at the Halo Sleep Sack) did not work on my kids; they would just break out. A swaddle strap worked really well because it has extra pillows over the arms to keep them from wiggling out. I explain the swaddle strap here: