Welcome, the 2011 Via 25Q seems quite popular! 33,000 miles, wow, I bought mine with 56K on it!
Regarding the antenna connections on the roof, there are several. There is one over the cab, in the painted part that looks like it's for a radio. I was going to attach a radio antenna there till I found out it is not needed, the dash radio and the coach radio both work fine and I suspect they are connected to the other radio antenna back by the holding tank vents.
Now there is another one you might be referring to and this one is located just behind the front cap on the white filon roof, it is a plastic roof jack for the satellite coax that comes out and connects to the dish, do you still have the dish? I removed my dish along with the plastic roof jack and cut off the coax. I've attached a photo that shows where everything was located (it's the center of the roof, my black kneeling pad makes it look like the edge) and a second picture where you can see the un-used radio antenna connection.
There are several 2011 25Q owners here, I bought mine in October of 2020 and have done a lot to the chassis and coach both in the way of repairs and improvements, there are a few things Winnebago could have done better but for the most part it's a pretty solid coach.
Make sure it's had the AEM performed, if not you have till October to get it done. You will receive an additional 48 months warranty on the emissions system plus some cash when you have it done.
For chassis issues or if you do your own maintenance I can answer a lot of questions but also join Sprintersource, there is a wealth of Sprinter information over there.