This might depend on where you live, in my area every inspector will check the roof (unless for some reason it's unreasonably dangerous to get up there).

Obviously they can't see hidden problems but the really bad stuff (cracked foundation with seepage issues, water damage, mold, etc) is worth looking into. My inspector pointed out a number of things like old cast iron plumbing, some unidentified venting, electrical that wasn't to code, insufficient ventilation to the attic, etc.

It didn't affect the price but it did give me a good checklist for what to fix in what order.