Once people start to texture their own new textures, the new style of normalmaps is Rome 2 is bound to be a bit confusing for those of us used to the purple-ish blue of previous total wars and other games. It has an orange-reddish tint to it, and attempting to load a traditional blue-purple normalmap results in a bugged texture that is completely unusable.
I'm still learning how to do it myself, so this tutorial is a bit ongoing. There's apparently an ATN filetype (Photoshop action) which the starcraft 2 modders developed that helps the process of converting blue-purple to orange normalmaps, but it also appears to be possible manually.
http://www.sc2mapster.com/forums/res...ple-to-orange/ - Gaddafy describes it rather well here.
http://www.sc2mapster.com/assets/sta...map-converter/ - This is the ATN file, but you don't seem to -need- it.
Simply put:
1) You create a Blue-Purple (BP) normalmap as usual.
2) Copy the Red channel and paste it into the alpha.
3) Then wipe the red channel completely blank as a white color
4) Do the same for the blue channel.
5) Resave it as a DX5 DDS and you should be good to go.
A mistake I did previously with this method was to copy the green channel for the alpha. You don't want to do this - if you run the green channel with the alpha channel (once you pasted the red channel into the alpha), you can notice how the red-alpha gives definitions which are otherwise lacking. When I was doing step 2 wrong (pasting green instead of red channel into the alpha) I'd get a glossy, smooth and normalmap-less texture. With it, you get the proper normalmap.
Ignore the wrong depth of the alphamap (the quilted portions being recessed). This was just a tenative test, because I was previously having poor/no normal maps, and this clearly shows the normalmap in use.