My baby is 8 weeks old, and has sporadically from 4 weeks, tipped himself onto his side, but not able to roll further, but will sometimes be able to tip back onto his back. As a result, I have been advised to have his arms out when sleeping. I am trying to find a suitable sleeping suit / bag to purchase, and not sure which one. Am I understanding correctly that the sleep suits should not have zips or Velcro? The bonds wonderbundle has zips but it states on the bonds website that it is sids approved, so is it ok to use?

It is important, once baby is rolling to have arms free.
Red Nose recommends that once baby is rolling they need to be moved to a cot & cease wrapping.
It is important that baby has the space of a cot & arms free to roll safely.
A safe sleeping bag, with arms out, may now be appropriate.

Infant Sleeping Bag
An alternative to wrapping is to use a safe infant sleeping bag; one with a fitted neck and armholes that is the right size for the baby’s weight. Clothing can be layered underneath the sleeping bag according to climate conditions.
https://rednose.org.au/article/wrapping-babies

It is a very individual choice what type of clothing or bedding that you choose.

A sleeping bag with arms out (with or without sleeves) is suitable, as is a sleep suit like the one you mentioned from Bonds.
There is no problem using velcro or zips as long as the whole product fits properly, is the right size for baby, does not restrain baby’s arms & there is no risk of baby’s head & face being covered by loose or poorly fitted. If using a product with zips, ensure there is no part of the zip that may detach or come loose.