Product warranties can cover a variety of shingle defects such as thermal splitting, some cases of granule loss, cupping, and curling. Warranties are usually for materials only, and not labor. So if you do receive new roofing materials due to a faulty product you will in most cases have to pay a roofer to install the new materials.
Incidental and consequential damages are damages that occur inside building structures due to faulty roofing materials. These damages are rarely, if ever, covered by manufacturer warranties and are usually the responsibility of the homeowner or the insurance company to repair.
Natural disasters such as hurricanes, tornadoes, hail storms, and high winds in excess of 50 mph are not covered by the manufacturer and are usually an issue the homeowner has to take up with their insurance provider. Also, shingle manufacturers do not honor their manufacturer warranty due to improper installations. If you do have a roofing problem due to improper installation it is recommended that you contact your installer and inform them of the problem.
Most of the time manufacturer warranties are prorated and are non-transferable, meaning if you have a roof for 10 years and you have a 20 year warranty you will only be reimbursed for the remaining 10 years of the roofs original warranty. Non-transferable means that if you were to sell your house, the warranty would be voided and could not be transferred to the new homeowner.
As a homeowner it is important that you ask for and receive a copy of the manufacturer's product warranty before making a decision on which materials you want to use before replacing an existing roof.