Shingle the Roof
Work one pie wedge at a time, starting at the bottom. Double up the shingles in the starter row to provide the angle for the rest of the shingles. Work up to the top. For the first section it is okay if the shingles hang over the corner rafters. Make a chalk line from the peak down to the center rafter and use a circular saw to make a shallow cut all the way down. For the remaining sections shingles will need to be cut to match the roof angles.
Make 15 piles of four shingles each, lay your cut shingle on top of a pile, mark it and then use a saw to cut through all four shingles at a time.