Quick lesson on satellite issues. First of all, a cable type connection will not work. The satellite receiver sends power down the cable to power the LNB on the dish. If there is a cable type splitter in the cable, one side will work but not both or neither one will work. Using the dedicated cable is the best way to go. If you want to split the incoming signal, you will need a device called a multi-switch. A lot of the Winneguard connection have a power switch that turns on a booster for the roof antenna. When the power is on, the unit is switched to the roof antenna. When it is off, assuming you have a park carble connection outside, it is then switched to the park cable.
More than a few poeple, me included until the YMCA where I work had an expert tells us what was wrong, have made this mistake. If you have an outside park cable connection and an outside satellite connection, you should have two connections inside.