The last image of Red Nose’s swaddling information sheet shows a swaddled baby tucked into place on their back with a separate blanket. Is the addition of the separate blanket to hold the baby in place the safest option? I live in QLD so wanting to assess risks between overheating vs. baby rolling onto side/front during sleep.

Blankets are not recommended to be used as a restraint. This graphic shows how to position a baby in the cot (feet to foot) with blanket tucked in on both sides & foot to prevent baby wriggling under any blanket being used. This is to reduce the risk of head & face being covered.
Blankets(light weight)are only recommended to keep baby warm (as necessary) not as a restraint to prevent rolling.

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)