The cable running from his closet to TV is coax, not HDMI.
That's a little vague.
What cable? Cable as in Coax? Coax for SAT and cable/antenna?
However it is wired, sometimes it is best to just start from scratch, eliminate any poor wiring techniques, connectors, cheap cable, excessive runs etc.
If you buy your own cable, solid copper core RG-6 is the best choice, quad shield or Belden's tri-shield (best rated)
Some things are a given.
With rooftop you need those control wires from the antenna motor.
You need coax from the antenna to the receiver, wherever that is located.
Somewhere inline with that should be a splitter that has a coax running from the splitter to a "power inserter", which supplies 21 Volts to the antenna's LNB
If you want portable antenna flexibility, you need a way to "jump" the coax for a portable input.
Many of the trailers have the control wires, antenna coax and jumper in the bedroom closet. That may or may not be convenient.
There are many trailers that had the promise of being SAT ready but in reality, some of the cabling was never installed from the factory, or, it was placed in areas different then specified.
The Wireless Genie client should simplify installation.
If not wireless, each Genie client needs a coax run from the power inserter splitter.