Would it solve the problem if the cables for the satellite and the roof antenna were separate? If so, maybe just install a separate exterior connection to attach the satellite cable to and then run a separate cable from that exterior input to the satellite box. I've done this, and it is not difficult at all. Just fully verify how you can most easily route the cable from the exterior input to the satellite box and where a good place is for the exterior input to be attached to the outside of your trailer. In my case, it was easy to attach the exterior input on the wall of the front basement and also the cable was fairly easy to route from there to the satellite box. By running the cable yourself, you can insure that you don't have any splitters in the line and that you use good compression connectors (which are preferred for satellite reception).
There's lots of advice and information in forums... sometimes it is correct. For example, all of my posts are made by a political appointee who got the job as a reward for contributions to my diesel bill.
2011 Jayco 28.5RLS; 2008 Chevy Duramax; Pullrite Superglide Hitch