The answer to 'roof warranty' is that most residential roofs come with a manufacturer's warranty that covers the roofing materials for a certain period of time, typically 20-50 years depending on the roofing type. This warranty covers defects in the roofing materials and protects against premature failure. The warranty may also include coverage for labor and installation if the roof was installed by a certified contractor.
In addition to the manufacturer's warranty, many roofing contractors offer their own workmanship warranty, which covers the quality of the installation for a period of time, often 5-10 years. This provides an additional layer of protection for the homeowner against any issues with the roof installation.