Best low-slope roof system for 1:12
I have a large shed dormer on the back of my house that's started having some leaks, and I need to have the current roll roofing replaced. the dormer is 50x15, 1:12 pitch, with a stone chimney and 2 vent stack pipes (otherwise nothing special). There's a small section (about 3 foot) at the top of the 8:12 roof for the rest of the house, so there is a roof slope change to consider. The roof is high up off the ground (it's on the back, and there's a walkout basement), so it is not visible at all. I'd like to find a roofing system that will hold up well, hopefully be reasonably priced, and can be put on now, in cold temps. I'm in central Indiana, and the temps right now are highs in the 30s-40s.
I have an estimate to have the current roof torn off, 1/2" foamboard applied, with .6 EPDM, for $3300 plus any replacement decking. This seems a bit high to me, but I don't know for sure. Is this reasonable for rubber? Are there other options that would be better/cheaper?