Cut any tree branches that hang above or come within six to eight feet of your roof. Trim any large bushes or shrubbery that the squirrels can climb.
Check near the roof for any decorative trim or attachments. Remove any item that may provide roof access.
Place screens over the openings of your downspouts and gutter guards on the roof gutters. Cover the exteriors of your downspouts with polybutenes. These sticky materials will discourage the squirrels from climbing.
Contact your utility company about placing cone-shaped shields on any power lines that come near the roof. These devices will prevent the squirrels from traveling across the lines, but the shields must be professionally installed.