Normally the satellite dish comes with the mounting hardware for installation, if not 1" or 1 1/2" #10 screws will work just fine. To secure the cable you have several choices, uses cable clamps screwed in to the roof about every 12", secure with puddles of Dicor, or my favorite, use strips of Etrnabond tape. Tape holds well and is easy to use. Put butyl tape under the dish and cover to get a good roof seal and then use the Dicor.
Before doing anything I suggest you wash the roof first to make sure everything has a clean surface for sealing. Hope your project goes well!
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