Depends onthe map kinds and what kind of terraining you do. I tend to put some "wear" on the ground where likely paths would be, to sort of simulate that heavy traffic goes through the area. As far as roads go, again that depends on the theme you have for the map. Do keep in mind that roads restricts building space if it is a melee map. If its a village/city tileset map, why not?
-VGsatomi