Yes, if you replaced the batwing antenna, that cable goes to the little power supply (usually has a light and switch on it) first along with a cable TV connection (if equipped). It may be easy or hard, depending on where the pieces involved are located. Depending on the antenna that you replaced yours with, you may not even need that little supply. You can download the wire routing schematic's from the Winnibago site which may help.
You will have to take that plate off where it enters the roof (very carefully!!). Best case would be to add a "splice" (Barrel??) fitting right below that if the wire inside is in good shape.
(For example: My little power supply is right below the antenna so to replace that wire, it is only 2 or 3 feet.)
Makes and models etc are useful when asking questions like this. (Old antenna, new antenna, etc.)