My 3.5m old started rolling at 3m, so he is in an arms out swaddle. He has just started rolling in his cot and sleeps on his belly. We always place him on his back in the cot, then he seems to roll and sleep on his belly, is it okay for him to sleep on his tummy??

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 tummy.
This is not something that needs to be stopped. It is important to make his new environment as safe as possible.

What happens if you try to roll him back when you see him on his tummy?
Often, babies will just go back to their position of comfort.
How does he go with tummy time when awake?

Ensure that the cot mattress is firm & flat & there is nothing soft or loose in his cot.
Always continue to place baby on back to sleep.
Increasing tummy time when awake is helpful in building up his upper body strength.

Red Nose has the following information now that your baby is she starting to roll.

Give baby extra tummy time to play when awake and supervised as this helps baby to develop stronger neck and upper body muscles which in turn enables them to roll back over.
Make sure that baby is on a firm and well-fitting mattress that is flat (not tilted or elevated).
Make sure that baby’s face and head remains uncovered (do not use lambswool, doonas, pillows, cot bumpers or soft toys)

As babies grow and develop they become very active and learn to roll around the cot.
At this time, continue to put them on the back at the start of sleep time, but let them find their own position of comfort.
By this stage it is not necessary to wake during the night to turn baby over to the back position

Do not use any devices designed to keep baby in a particular sleep position.
https://rednose.org.au/article/what-do-we-do-now-that-a-baby-has-started-to-roll-over

My baby is 4.5 months old and has been rolling into her tummy alot the past week. We have increased tummy time during the day, made sure the cot is clear of any aids risks, however she continually rolls over onto her face.  During the day it seems to really bother her and at night I roll her back onto her back or try to turn her face to the side. But she keeps putting her face down I’m worried she will smother herself. Any tips?

Most babies will be rolling over by 4- 5 months. This is very normal as babies grow & become stronger.
Many babies then prefer to sleep on their tummy.
Always place baby on back for sleep.

This is not something that needs to be stopped. It is important to make her new environment as safe as possible.
Ensure that the cot mattress is firm & flat & there is nothing soft or loose in her cot, especially as she is face planting at times.
You can try to turn her face if you see her with face down, but often, like rolling to tummy, babies will just go back to their position of comfort.
Always continue to place baby on back to sleep.
Good to see you have increased her tummy time when awake - that is always helpful.
Are you still wrapping her? She needs arms free to assist with rolling.

Red Nose has the following information now that your baby is she starting to roll.

Give baby extra tummy time to play when awake and supervised as this helps baby to develop stronger neck and upper body muscles which in turn enables them to roll back over.
Make sure that baby is on a firm and well-fitting mattress that is flat (not tilted or elevated).
Make sure that baby’s face and head remains uncovered (do not use lambswool, doonas, pillows, cot bumpers or soft toys)

As babies grow and develop they become very active and learn to roll around the cot.
At this time, continue to put them on the back at the start of sleep time, but let them find their own position of comfort.
By this stage it is not necessary to wake during the night to turn baby over to the back position

Do not use any devices designed to keep baby in a particular sleep position.
https://rednose.org.au/article/what-do-we-do-now-that-a-baby-has-started-to-roll-over