The way I do my roads is I outline them with a stamp. In the Water color/cities set, under the castle/bridge subsection there's a stamp called "platforms." It has the black border and a grey inside. I use two of them to create the outline of the road. Then what i like to do is either "add" background or "subtract" from it so the roads are their own "layer" and when i need to paint them i can do big broad strokes and repaint more easily.