It is protein and B-complex vitamins that vegetarians might need for their health and might be willing to eat, that is going to exist whether or not it is eaten and that otherwise would be wasted by humans, from species most people have never tasted before and might find interesting: deer, squirrels, possoms, raccoons, birds, etc. Eating roadkill is not a new idea, but creating a government-compliant supply chain for it, high-quality sterilization and cooking procedures, and selling it in supermarkets might be.
From PETA: “If people must eat animal carcasses, roadkill is a superior option to the neatly shrink-wrapped plastic packages of meat in the supermarket.\ Eating roadkill is healthier for the consumer than meat laden with antibiotics, hormones, and growth stimulants, as most meat is today. It is also more humane in that animals killed on the road were not castrated, dehorned, or debeaked without anesthesia, did not suffer the trauma and misery of transportation in a crowded truck in all weather extremes, and did not hear the screams and smell the fear of the animals ahead of them on the slaughter line. Perhaps the animals never knew what hit them….”
A few challenges: finding people who know how to properly butcher a variety of wild animal species, the meat still would need to be packaged, some Tibetan Buddhists think that there are physical signs that consciousness has left a body for which one should look, people who collect the meat might encounter animals that are only injured or not quite dead and may need to call a veterinarian or sit with/near the animal until it dies, finding a network of spotters (perhaps commercial/personal drivers could be paid a small amount for reporting roadkill, though not so much that the payment might incentivize people to kill animals intentionally), and transporting meat from possibly rural areas to processing facilities quickly enough.
(This idea is released under a Creative Commons Attribution 4.0 International license. It may be used commercially.)