Resale inspection of roof

How do they inspect the roof these days, do any use drones?

They have a specialized tool that is rest against the house and provides steps for the inspector to climb up to the top of the roof to visually inspect it. A ladder.  ;D

and use said ladder to get into the attic (leaks are easy to detect, so i've been told)

Yes, most home inspectors will use a ladder and go into the attic to inspect the roof and some will even use a drone to inspect the roof. If the home inspector sees any issues with the roof, they'll note that in their inspection report and recommend that the buyer have a roofer come out to further inspect and provide a quote for the necessary repairs.