I had the manual version of that one - it was standard definition. I believe, if it mounts the same (I don't know why it wouldn't), the cable comes down through wherever you want it to. Mine had a flat plate mounted a few inches away from the base of the satellite for the cable to go into the class C I had. The cables that are attached to the satellite will be long enough for it to swivel around and find the satellites. For my class C, the cable was just run into the roof and around to where it needed to go near the TV. I am glad I didn't need to run that cable. If you have an external cable-in connection on the outside of your trailer, you could just have the input from the roof go into that connection - that is what I do now with my portable. If you are going to mount the satellite on the roof, you could try to mount it directly above where your TV currently is so you can just drop the cable down to it.
As far as advise, I just went through buying a satellite for our new trailer. You may have already thought about these, but I will post my opinion anyway just in case. If you park your trailer somewhere, and a tree is in the way of your roof mounted satellite, you only have a couple of options - cut the tree, move the trailer, not watch TV. A second thing, IF you decide to sell your trailer anytime in the future, you will not get the money back for the satellite attached to your roof.
Now, if you have the mobile satellite, not mounted to the roof, you can move it around and possibly get reception - instead of cutting the tree, moving the trailer, etc. If you sell the trailer, you can keep the satellite for the next RV you buy, sell it, give it to someone, or keep it and use it somewhere unexpected - in-laws in my case. I gave up the HD so I could keep the convenience.
2014 Jayco Jay Flight 32 BHDS
2015 Ford F-250 Lariat 6.7L Powerstroke 4x4