It sounds like you have a Winegard Trav'ler which will work for either Dish or DirecTV but not both depending upon the model installed on the roof. If you are sure the previous owner was using Dish Network then you are good. If he was a DirecTV customer you will have to have some modifications done to the antenna in order to work with Dish.
Assuming that it is a Dish Trav'ler you will want to look for a cabinet where there is a disconnected HDMI cable and an unused coax cable. It "could be" where the Trav'ler controller is located but does not need to be. Just to confirm you have a Trav'ler, you should have a black box with a digital display and 3 buttons on the front that read Power, Select and Enter. You push and hold the power button for 3 seconds and release. The display will then read if it is Dish or DirecTV and the antenna will raise up and lock onto the satellite even with no receiver connected.
The receivers Sat IN will be a coax connection and that's the line to the antenna on the roof. The output on your receiver should be HDMI if you are using a 211 series or DVR receiver. This will send the HDMI signal to the TV's. You use the TV INPUT selection at each TV to change from TV/Cable to the selected HDMI input.
I know that more info than you were looking for but hopefully it will get you a good start. If you have a multi-meter and you can get up on the roof I can also tell you how to trace the coax coming from the antenna but just finding the loose coax cable and setting the TV to the right setting should allow you to see when you get the right coax.
What I post is my 2 cents and nothing more. Please don't read anything into my post that's not there. If you disagree, that's OK.
Can't we all just get along?