Researching roofing companies today is easier than ever. First begin with how many reviews the company has on line at Google, Angies list, Home advisors and Facebook. A company with 500+ reviews and top tier rating is preferred. Read the reviews to determine if there is any commonality with over promising, installation problems or communication. Reputable companies will happily provide you with a Workers Compensation and General Liability certificate. Take that certificate a step further and call the insurance company to ensure the policy is up to date. Make sure you not only focus on the labor warranty but more importantly the Manufacturer's warranty. You should receive a written warranty from the manufacturer specifying the exact warranty that was purchased for your home and installed to the manufacturers specifications.