World painter might be what you need!
It makes custom terrain but requires a little getting used to first!
As for the roads, try singleplayer commands, it has world edit built in.
Thank you, but I'm building the roads by harvesting materials and then laying them down where I want them to go. I just need an easier way to plan my routes before I start building each next section of road. Don't want to have to tear up a bunch of blocks and fix them.