Condition or provenance of the roadkill is highly important. If it is covered in flies or maggots or other insects I would recommend a Rioja.
If it smells like rotting flesh it is probably what is known as a little "high" and a Cabernet Sauvignon is the match for this meat. If its eyes are clouded over white it's probably not too fresh (though likely still edible)and while most wine connoisseurs would choose a Merlot in these circumstances, my recommendation is a good Pinot Noir.
If there are fleas on the animal its normally a safe bet that it's still edible and its got to be a Claret every time. If it's completely mangled, it's probably not worth a fine wine. A beer of the Pale Ale type will accompany this type of dish adequately.
Rigor mortis (when the animal stiffens) sets in pretty quickly. Most of the animals we've eaten have been stiff and a Chardonay has always seemed a good match for this meat. There's no reason of course to assume the animal is spoiled just because it's stiff.
Rabid animals. Invariably a cold Chablis. You may want to use rubber gloves when killing, gutting or skinning rabid beasts, or at least make sure you don't have any open wounds on your hands or any other skin that touches the animal. Rabid Raccoons, Skunks and Foxes usually fall into this meat category.