There are mechanically seamed standing seam metal roofs that can be used at that low pitch.
Todd Miller
2011-12-11 03:00:10.000000
+1
At that low a pitch, your choices are limited in metal, or any roofing options for that matter.
Mechanically seamed standing seam or a soldered metal roof are your only real options here.
If you want another type of roof aesthetic, you can add slope to an existing roof but it can be difficult depending on how cut up the roof is.