My baby has started to roll but still has a startle reflex. What should I do?

How old is your baby?

Red Nose has the following information when baby starts to roll.

Ensure that the cot mattress is firm & flat & there is nothing soft or loose in the cot.
Always place baby on back to sleep.
Increasing tummy time when awake.
https://rednose.org.au/article/what-do-we-do-now-that-a-baby-has-started-to-roll-over

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

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.
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

Ensure that the cot mattress is firm & flat & there is nothing soft or loose in the cot.
Always place baby on back to sleep.
Increasing tummy time when awake.
https://rednose.org.au/article/what-do-we-do-now-that-a-baby-has-started-to-roll-over