Even with a level 1 map_heights and a completely zero map_roughness it still generates a rolling terrain. I somewhat confused at this one myself.

I thought that there might be a text file that would determine the relevant heights, but the landscape on a particular tile is always constant - which suggests that it's referencing a graphic.

Another question is where does the game get the information for the background on the battlefield from? The battlemap tile itself comes from the textures in the data\terrain\battlefield\, I tried changing the textures used on the aerial map with no success. The shape at least must be referenced from the battlemap somehow because we get offmap models and geographic features.