Here are a couple of quick ways to make roads and water.
In the first method I use 3Ms indoor/outdoor tread. It's 1" x 5 yards at about $9.
I like the texture and the look. Even unpainted, it looks like a road.
Another method I use is paintable sealent. I spread it out on silpat, a flexible baking sheet, and let it harden overnight. The following day it's ready for painting and flocking.