While not strictly speaking necessary, we believe this is far and away the best choice. For one, if you pick the right manufacturer, you know you are getting quality materials from the bottom-up. Also, a roof is actually a system, not just a bunch of shingles nailed to plywood. All materials from the same manufacturer means everything works together to keep your home protected.
Another danger to using materials from multiple manufacturers: if something does go wrong with the roof, you might end up with a nightmare scenario where everyone involved points the finger at the other manufacturer as the reason for the failure. The safest choice is to go with one manufacturer for all your roofing materials and have it installed by a certified installer. That way, everyone is on the same team.