Yes, just use a road texture as the terrain. If you mean with curbs and sidewalks and stuff, then no, you'll have to model them for them to look any good.
Also, you'll need two road textures, one for each direction the roads travel in. If you want non-square shaped roads, and turns that aren't 90 degrees, you will also need to model them.
One last note, the detail texture is displayed over all the terrain, so your roads will also have the detail texture. This isn't a big deal if your road is made of asphalt or rock or something, but looks odd on some other textures.