Overview:
Roll roofing can be used on roof slopes as little as one inch. Roll roofing is less expensive then other roofing materials with a less attractive appearance. Roll roofing is made of the same material as asphlt shingles. Roll roofing can be applied with exposed or concealed fasteners.
The link below is for the installation of double coverage roll roofing.
http://gaproofinginc.com/pdfs/apps/app_doub_roll.pdf