My 1 week old struggles to settle in her bassinet, so occasionally we let her sleep in the bed with us so everyone can get some sleep I follow all the safe sleeping rules for co-sleeping but always wake to find she has rolled onto her side - should I roll her back into her back every time? This normally wakes her as she has her arms out she startles herself awake

Red Nose recommends that the safest place for baby is in their own sleep space.

Red Nose co-sleeping information has the following:
Avoid co-sleeping with baby less than 3 mths of age

Is you baby sleeping in the middle of the bed or on the side?
Is the mattress firm?
Do you have soft/loose bedding?
https://rednose.org.au/article/is-it-safe-to-sleep-with-my-baby
https://rednose.org.au/downloads/RN0493_23_Co-Sleeping.pdf

Have you had a follow up visit with your Midwife or Maternal/Child Health Nurse?
Can you discuss settling techniques with them?
What State are you from? There are some phone support services in each State I can give you.
Also check out Red Nose settling information.
https://rednose.org.au/article/settling-information-statement