Choose the material of the roof panels. A variety of options are available including PVC, wood, fiberglass and polycarbonate.
Measure the square footage of the pergola top. Purchase enough roof panels to cover the area.
Cut the panels to the pergola's length. Add 3 inches on the top and bottom to allow for a slight overhang.
Attach the panels one at a time using screws. Start on the left side and work your way across the roof. By doing so, it will ensure that the panels line up. The panels should overlap each other slightly.