a metal roof is not usually classed as fragile, so you only usually need edge protection (eg scaffolding), unless it has skylights in the roof, which would be fragile and fall protection would be needed for them.
tbh though if you're competent to do this work then you should know this really, if you don't know it then I'd advise you get a specialist safety consultant on board to guide you through it.
Or use 3/4 inch shuttering ply as a cover over any hazards , Like they say prevention is better than a cure !
This one was a single skin on the bottom with rock wool and cross purilins then another single skin on top , i think it is called a stitched roof in the trade .
The ply alone for this one cost just shy of ÂŁ2000 without the scaf and loader .
So i hope you ( Woko ) have a contingency fund in place if you have not accounted for bits like this when quoting .
PS , that is not a dig ! It is easy to get caught out , on this job alone both myself , my structural engineer and the building owner misjudged the depth of the space between the two sheets and i had to overnight near on ÂŁ3000 ( at my expense ) worth of new fixing in from Germany to get the job in before the December crash !