@Clarkie
Morph Brush, blimey, just export a super high resolution square from Blender and then paint your roads and valleys live in the viewport in Poser!
Doing that, you can place buildings and trees first, then literally sculpt your roads perfectly around them in the scene.

And to make it easy and even cooler to use, just draw a map of your road in GIMP and apply it to your imported high resolution square inside Poser, then use the Morph Brush to paint directly onto it where you drew the roads.  Not only do you get Vue-style terrain painting in Poser, but you can even see where you're supposed to be painting the roads due to the map you applied as a guide.

Noodle, mate, noodle ;-)

@Vilters
1, 3, 2, and then 1 again.