The roof covers everything, but will be passed by an inspector if "it's not
currently leaking". Get a look-see yourself for apparent stains on the rafters, and don't rely solely on the inspection.
If a shingle roof is 15 years old, you'll probably need to replace it soon for one reason or another. If you're present during a roof inspection, point out the stain(s). The inspector will likely give you a
hummana-hummana-hummana answer. Obviously, I'm very dissatisfied with my many roofing inspections. One roof that showed obvious DIY repairs got passed, yet leaked in the middle of a bedroom upon the first rain.
Use the roof inspection and other inspections of the house as bargaining chips to lower the price, so as to allow for DIY repairs or to defer repairs (or
your selected replacements) for a later season.
.