Deter pigeons from roosting on your property by placing chemical bird repellent in the spots where birds have a tendency to roost. The chemical bird repellent most commonly used is called "Bird-X" and is readily available from online retailers. "Bird-X" is recommended by the Audubon society as a safe way to deter birds from roosting or inhabiting personal and commercial property.
Use stainless steel wire netting to turn a level surface into a sloped one. Cut the wire netting with wire cutters and use zip ties to secure it to the surface you are modifying. Attach the wire netting anywhere birds are likely to roost, such as rafters, awnings and ledges.
Place live traps anywhere on the rooftop pigeons have been spotted. Bait the area where you are planning to place the live trap so that the pigeons will associate the area with food and be attracted to it. Place the live trap down and leave the door open for pigeons to enter and exit freely. Set the trap doors to close a few days after you first set the trap. A few pigeons should be trapped inside, and their presence will attract more pigeons. You may choose to relocate the pigeons after they have been trapped, but sometimes they will just fly back to the place they were trapped unless other deterrents are put in place.
Place spike strips along the edges of the roof. Pigeons are deterred from landing on a roof protected by spike strips because they use the same logic a human would. The strips can be fatal if a bird crash-lands into them. Check the strips daily for any dead birds that may not have seen the danger before making an attempted landing.