I had this same problem too, but realised that the reason why it wasn't working is because I didn't unpack it properly and Radious_Total_War_Mod within the RTW2 Mod Manager needs to be ticked. If you don't have the Mod Manager, then I suggest you get it since this is what caused me several minutes of headaches trying to figure out what is going wrong.

Summary:

1) Download the complete Radious Mod

2) Download RTW2 Mod Manager (The updated version already has this).

3) Follow Radious's instructions on installing his mod by placing each file into the specific folder i.e. C:\Program Files (x86)\Steam\steamapps\common\Total War Rome II

4) Open RTW Mod Manager and tick the Radious_Total_War_Mod out of the list

5) Click Launch and it should then come up with Steam. Click play and "hey presto!" it should now work.

Alternatively, if you still have problems getting the Radious Mod to work, simply follow this 1st link below and watch. http://www.youtube.com/watch?v=5pOnq1uzxRo

or this: http://www.youtube.com/watch?v=juwlhsKd0yM

Hope this helps you bud.