Here's the checklist that I use to inspect a roof during a home inspection.
The checklist includes several items that a home inspector may check during a roof inspection. This inspection procedure goes beyond the scope of a home inspection according to the Home Inspection Standards of Practice.
Check the roof covering.
Check for an offset pattern.
Check the drip edge.
Check the slope.
Check the roof ventilation.
Check the fasteners.
Check the deck sheathing.
Check the underlayment.
Check the ice barrier.
Check the flashing areas.
Check the nail penetration into the deck sheathing.
Look for indications of an active roof leak.
To learn about those roof items and how to inspect them during a home inspection, home inspectors and homeowners should visit https://www.nachi.org/introduction-home-inspection-course.htm and take the free, online "Introduction to Home Inspections Course."