IF your dish gets a direct hit, it will blow out the roof no matter if the cables run through it or not. Grounding a dish doesn't protect from lightning strikes it reduces the chance of the dish getting hit by lightning. By correctly grounding the system, ie utility ground within 15 ft of the service meter, this greatly reduces the potential resistance difference between the earth and the static buildup on the dish. the ground wire dissipates the build up back to the earth. By no means does it increase the potential to be hit. Also on this note if the ground for the house is incorrect, not buried deep enough to meet the earth's potential, anywhere between 4 and 12 ft, depending on soil content, water table, etc. Most requirements are 6-8 foot ground rods, than the dish's ground could pose the difference attracting potential energy