This is a very broad question due to the large number of roofing products available, types of damage that can be sustained, and definition of damaged. The easy answer is let us take a look at it and we can help you determine. Roof damage can range from actual loss of shingles to more subtle damage such as granule loss.  Generally, one can look for irregularities in the roof planes such as cupped shingles, high or low spots, light or dark “splotches” on the product itself, excessive granule accumulation in gutters or downspouts, or wet spots in the ceiling.  Roof damage cannot always be seen from the ground and often needs a trained eye to detect.  If you have something you suspect send a photo and question to info@brinkmannquality.com