Hi I have a 4 month old who is showing sign of rolling. They have previously been in the love to dream bag and now using the transition bag with one arm out for last few days which has interrupted their sleep due to them waving their arm around and waking themselves. I took both arms out today and it looks like they still have some startling reflex so was going to put arms back in tonight so we can both sleep just worried about signs of rolling ie head tilt, legs up and over. Any advice ?

Most babies will be rolling over by 4- 5 months…...some earlier, some later. 
This is normal as babies grow & become stronger.                         
Many babies then prefer to sleep on their tummy or side.
This is not something that needs to be stopped. It is important to make the environment as safe as possible.

It’s essential to stop wrapping as soon as baby starts showing signs that they can begin to roll, usually between 4-6 months. If you wrap baby, consider baby’s stage of development. Leave arms free once the startle reflex disappears around 3 months.

If you are using a bassinette, it is time to transfer baby into a cot as soon as they first show signs of being able to roll.
It’s essential to stop wrapping as soon as baby starts showing signs that they can begin to roll, usually between 4-6 months. If you wrap baby, consider baby’s stage of development. Leave arms free once the startle reflex disappears around 3 months.
https://rednose.org.au/article/what-do-we-do-now-that-a-baby-has-started-to-roll-over

Baby needs arms free & the space of a cot to roll safely.
**Always continue to place baby on back for sleep.

Red Nose has the following general information now that baby is rolling.

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