Know a guy who is on all the road kill deer lists. The meat isn't very good. Sometimes it isn't all that great even in Summer sausage.
When I lived in Florida, one of my friends used the highway as almost the only source of animal protein for his family. He would pick up pretty much anything, from Deer to Opossum, to Raccoon, to Dog, to Snakes.
It all tasted good, if it was prepared correctly.
The same rules apply to roadkill, as they do to other meat: If it's bad meat, it's bad meat. Putting it in a summer sausage won't magically turn it into meat that didn't spoil. If it's trash, it's trash. The source doesn't matter.
But if it hasn't spoiled, it's free venison, that will taste just as good as any other. (plus, it's pre-tenderized