I seldom see flat roofs. Can flat roof membranes be easily damaged by walking on them in temperatures well below freezing? (I’ve not yet seen this particular roof and have no idea if it is modified bitumen, TPO, PVC, …)
Sweep some of the flat roof off to figure out what you have. A BUR can have rock ballust on it but so can a membrane. If it’s a membrane it can be damaged just like in the summer months. If it is a PVC it can be walked but stay back from any penetraions. It should have a cant strip to make the corner solid but sometimes they “forget”. if you step in those areas you could create a hole and a ticked off client/seller.
Take some courses.
Yes you can walk on them just fine.
Most are modified bitumen.
Which would you suggest BUR or a membrane?