When you find a turtle on the road, you should move it off the road in the direction it was traveling. Removing a turtle is not only illegal but deprives the turtle of its home and ability to make more turtles. Turtles have a home range and given the opportunity, will do everything they can to escape and go back home.
If you post a small jpg photo of the turtle, I may be able to identify it. If you go to enature.com, you can see the turtles native to your area by putting in your zip code (or they used to have that feature). As for what it eats, see
http://www.fishpondinfo.com/box.htm if it's a box turtle and
http://www.fishpondinfo.com/turcare.htm if it's an aquatic turtle. Box turtles have the ability to fully close themselves into their shells via a hinged plastron (bottom shell hinge in the front). If you're in the desert, it could be a tortoise too. If you provide photos or a description, I could tell you more.