It is important to note that home inspectors are never required to walk on any roof.  Inspectors must inspect the visible portions of the roof but are not required to walk it.  That means that sometimes we use a ladder at the eaves, binoculars, or even a drone.  We will do the very best we can for you, but sometimes, we do not walk on a roof because we all want to go home safely to our families.  It is up to each individual inspector whether they feel they can safely walk on a roof or will use other inspection methods.  Common reasons for not walking on a roof include:
Too high
Too steep
Slippery conditions like snow, ice, frost, wet wood shingles or shakes, wet metal roofing
Tile roof - fragile
Just to reiterate: a home inspector is never required to walk on any roof.  We must however, inspect the roof using other methods if not walking the roof.   We estimate that we walk 90% or more of roofs.