Is the edge protection made up of tube and fit scaffold or key clamp type posts? Who installed it (if installed already)? If you had a company install for you then they should be able to provide you with details and possibly someone who is deemed competent to inpsect it. I would suggest treating it like scaffolding and have it inspected weekly as a minimum and keep a regsiter identifying it has been inspected. Can be inspected by soemone who has undertaken a scaffold inspection course. Would also look at inspecting each time it is exposed to conditions likely to cause deterioration e.g. following adverse weather conditions or following substantial alteration.

I agree it would depend on how often the roof is used, if not that frequently then obviously weekly is probably not required. Just trying to provide a starting point and perhaps they can work out from that what best suits.