Uploaded new version 0.7.11.3054 that (probably) fixes the issues with roads on ATI 4xxx and 3xxx cards. Please test if it resolves the issue for you.
I must say that this is one of the most absurd bugs I've ever encountered, that took me a couple of days to locate. Simply said, roads sometimes weren't rendered at all, or were rendered randomly only in some terrain tiles.
After a painful search I've narrowed it down to a single shader variable, and the fix consisted of giving it a name that works. The variable name can be (almost) arbitrary, but for some reason the GPU didn't render the roads if that particular variable was j6 or mare_1 or many other names, but it worked if the name was frcm_1. If it doesn't make any sense to you, you are not alone.
Understandably, it cannot be taken as a proper fix, just a workaround until the drivers are fixed.