First a question: Your roof-top antena is it a DOME, or is it a ROUND dish or is it an OVAL dish?
Dome/Round dish can see satelite 101.. This is used for DirecTV (SD not HD).
Call DirecTV, Tell them you want to set up an RV account, get transferred to King dome,, Hang up
Call back, do it again
Call back and tell 'em "You transfer me to King Dome I'm calling Dish" and they will get you to someone who can set it up for you.. That simple.
IF you have a OVAL Dish with an odd looking extra wide LNB... Odds are this is a DirecHDTV antenna.. Now there are 3 kinds of those. and you need to know just which yours is.. Contact the antenna maker to find out.. then
See above.