Don't know what part of Utah you're in, but if you're looking for roadkill snakes, I can tell you I've seen a few up here in Monument Valley. No one here will touch them. Taboo for Navajo. I saw a huge one in the road on the Hopi rez. But you have to make sure it's not a Horned Rattlesnake or some of the other protected ones. Those are illegal to possess parts of.
The Hopi catch a certain kind of rattler for the snake dance. Yeah, they dance holding the live snakes. But that dance is closed to everyone but the Hopi. Hopi tribal police have the roads into the village blockaded when it's going on. So, anyway, you'll find a lot of rattlers in this region because they're taboo for the most part to fool about with. But the other issue is the rez has its own laws regarding animals. But find the rez line near Monument Valley and I bet you find a few in the road. That's where I've always seen them on the road near Mexican Hat.