PECIALIZING IN RESIDENTIAL, FLAT AND COMMERCIAL ROOFING. Thank you for considering MAGNUM ROOFING for any and all your roofing needs. At MAGNUM ROOFING we bring 34 years of business experience with us and provide superior workmanship with competitive pricing. Please visit our products section for information on the different brand products we offer.You will notice that GAF now offers an architectural shingle with a lifetime warranty. The Weather Stopper System Plus Warranty from GAF is the first warranty in the business to provide a 50 year, non pro-rated warranty on both material and labour. It is the best warranty protection in the business.