Here are the two best techniques for roof installs and bringing cables into the attic;
DBS ROOF INSTALL TECHNIQUE
I install a lot of roof mounts on pitched asphalt shingle roofs. I never never use silicone or roofing cement or coatings. And, I never use those lag screws that require predrilling.
I use #14(1/4"dia) fully threaded hardened hex head drive sheet metal screws. I drive two three inch long ones into the rafters and four 1-1/2" long ones into the corners of the feet. It is not difficult to find the rafters, since hitting the roof surface with the back of your fist will result in a solid sound. Even if you miss, six fully threaded screws will provide a very good hold that will require a hurricane or a tornado to blow off. In that case, the home owner's insurance will apply, since it will be considered an "Act of God."
The above provides for one solid mount. The screws driven through the shingles, without predrilling, provides a near perfect seal, since the heat generated in driving them melts the asphalt, which rehardens around the screw. This is also basically how roofing nails work. Just for insurance and for those customers who inspect the install, I cover the heads with a pliable modeling clay like duct seal. A one pound brick costs no more that $2 at Home Depot. This is also perfect for sealing cable wall entries.
The best level that I have used is the Israeli made Post-Rite sold at Sears for $5.99. It is a post level with two bubbles spaced 90 degrees apart on a vertical hinge. The magnets don't work that well, but the elastic strap holds it firmly on the "J" pole. It's worth having, if you do a lot of installs. Forget the bubble level that fits on the inside of the mast. It requires you to get up and increase your center of gravity to look at it from the top, which can be dangerous on a steeply pitched roof. With the Post-Rite, you can do everything while sitting on the roof's surface and still have access to see the levels, without moving your position above and back down to the mounting.
The center of the dish mounting foot is usually marked with an embossed line down the center. Except for a very old mounting foot, one of the center holes is round, and the other is a slotted arc. The first step is to screw in the long 2-1/2" to 3" long screw into the round hole, just driven down enough so that you can pivot the foot on this one screw. Swing the pole up and down and pivot the foot until both bubbles on the Post-Rite are centered. Drive in the second lomg screw. Then, drive in the short corner screws until snug. Using the bolts and nuts that hold the pole to the foot, tighten them for a final adjustment, if plumb had shifted a little due to the roof shingles having been compressed from driving in the screws. Use small balls of duct seal the size of a small marble and work them over the screw heads.
Set the skew or tilt and elevation correctly on the dish correctly for the locality. Place the dish back on the pole and tighten the vertical clamp bolts just tight enough to take up all of the wobble. Swing the dish horizontally until you get the highest signal levelon the meter. Tighten the vertical sleeve mounting bolts. Check the TV to verify signals for each satellite position.
Removal of Dish Mount
Backing out the screws leaves holes of less that 1/4" that are almost undetectable to the casual observer on the ground. The mounting foot is not "glued" to the shingles and comes off without tearing them. Whoever thought gluing the mounting foot to the shingles provides security is a fool. If the wind blows the dish off in a hurricane, a lot of shingles comes off. If held only with screws, a dish blown off results in less damage. The duct seal is great for sealing the holes left from the removed screws. Filled holes can be very discrete.
If you are removing a previously "glued" mounting foot, the way to do this with the least damage is with a thin stainless steel wire, such as aircraft safety wire or a piece of piano wire wrapped between two sticks like a garotte. Saw away the silicone with the wire, and the mounting foot comes off pretty clean. I're even used this method to take off mirror tiles stuck to dry wall, without damaging the surface.
If you are replacing shingles, the dry wall knife is your best friend. It allows you to lift the heat activated glue down tabs of asphalt shingles without breaking them off.
How to install a roof cable entrance.
I'd go out and get a piece of 1-1/4" PVC conduit, a couple of same size 2 hole clamps, a service entrance head, and a vent flashing.
Go into the attic, using a 1-3/4" hole saw. Start it flat with the sheathing right next to a rafter. As it it cutting part way through, tilt the hole saw, until it is plumb. Outside; using a large putty knife or a dry wall taping knife, carefully lift the shingles around the hole. Remove any roofing nails at least a foot radius around the hole. Place the flashing over the hole, and cut a circular "U" out to match the flashing raised area plus 1 inch all around, starting at or below the center of the hole. Slide the flashing under the shingles, matching the raise area. Shove an 18 inch long piece of pvc conduit through the flashing and the hole in the sheathing. Inside the attic, strap the condiut to the rafter. Outside, nail down the bottom corners of the flashing and replace any nails taken out that held the shingles. Glue on the cable entrance weatherhead.
This is the correct and truly professional method of doing this.