Get on top of your roof via the ladder. Decide how to lay the roll roofing. If you can maneuver easily around your roof, you'll want to lay the roll roofing horizontally. If your roof is particularly steep, you'll want to lay it out vertically.
Measure the width of your roll roofing and then measure the same width on your roof, starting at the eaves (overhangs) on the edge of the roof.
Snap a chalk line along the roof where you just measured.
Place the end of the rolled-up roll of roll roofing at the edge of the roof, along the chalk line. This is where it helps to have an assistant.
Slowly unroll the roll roofing. Make sure to keep it taut. Hammer in a nail on either side of the roll roofing every three inches.
Keep the roll straight as you unroll it. Continue to do this slowly. If any creases appear, remove the closest nails and pull the crease out of the roll before renailing it.
Hammer a nail into the portions of the roll roofing that hang over the eaves. Do this every three inches as well. You can now install your next section of roll roofing adjacent to the section you just installed.