A roof is much more than a series of shingles and not only are there multiple levels of a roof but there are also a number of other, smaller components that have the potential to require roof repair  if a home owner is not sure what part of a roof might be impacted and the cause of something like a leak there are a number of diagnostic procedures that a roofer can look into such as whether the metal flashing has failed which would allow water to come inside the roof. The flashing should be inspected at least every year to ensure it's not going to need repairs.