We always use a membrane system, but we use modified bitumen, a.k.a. SBS. It is sold as roll goods, (NOT roll roofing) and comes in about 5 colors from different manufacturers. If you know what you are doing, you can put this stuff down cold and not have any problems. We put it on 0 slope roofs all the time in cold adhesive as our city is frowning more and more (as are our clients) on our noisy, smokey, sulphur belching kettle.
But if you are forced to use shingles by a deed restriction or city code, then there is a way. Cover the whole roof area in self adhering/self healing ice and water shield over 15# tin capped felt. Then nail your shingles on. The shingles are cosmetically more pleasing and are UV resistant. The ice and water is uglier, and has no UV resistance (unless the half lap kind), but it will "heal" around the nail holes.
Do yourself a favor and have someone with experience do the tie in to the existing roof. I sure make a lot of money fixing those...
Robert