Ten minutes with a pair of binoculars in early autumn is worth more than any callout in January. Here is the order we work through it in.
Start from the ground and work up. Look along the eave line for sagging gutters or a run that has pulled away from the fascia, because that is usually the first visible sign of a fixing that has let go. Then look at the field of the roof from three different angles — granule loss reads very differently in raking light than it does at noon. Check the flashing around anything that penetrates the roof: chimneys, vent stacks, skylights. Finally, look in the attic on a bright day with the light off. Daylight where there should not be daylight tells you more in five seconds than an hour on the roof.