Greebo,
There is an order of tasks for laying down cosmetic only roads\rivers or AI resupply. First get all your topography squared away, then lay in all objects like fields\strats\ports and so forth. I'm going to install the GV spawn paths before thinking about roads but, I will have to lay down rivers becasue I need bridges. So I'll have to create some quick local blueprint maps for paths at each field or come up with a standard repeatable arrangement.
When you setup a river or road that is only cosmetic, lay them down, tweak them until they are what you want. Only save them if you have to walk away, don't be tempted to build to look at them offline. When they are tweeked into place, save and run the mask. When it's done check to see that it removed trees and bushes. Then run build to check it out offline.
After that if everything is how you want it, do the create all for roads and tracks to lay in the resupply system. Same thing, tweak them all into place and only save if you have to walk away. Then when you think it's all in place, run mask, then build. Yes Hitech...irritating....
Here is a test today from my micro hill test terrain. This area is 6 mile diameter wich is the average for all fields, inside of which I applied a micro hill texture for tank combat. I will be applying things like this around feilds with GV spawns now to make tank combat more interesting.
Those dark blobs on the ground under the road to the left where it curves to the right across the hill was where trees stuck up through the road before I ran the mask. What tank ace in this game in his right mind is going to drive around out in the open on an exposed road. Buttttt.....waaa we want cosmetic anything and everything...waaaaa.....