En el foro oficial parece que hay algunos más con problemas similares al tuyo, de momento están esperando respuesta de CA.
forums.totalwar.com/showthread.php/10978...28WITH-MDMP-FILES%29
Si quieres puedes poner un post en ese hilo añadiendo los datos que te piden...
Algunos han puesto que han resuelto el problema reinstalandolo todo incluido steam.
Esto es lo que piden los de CA para poder ayudarte.
• When posting your issues please respect the following: one thread per issue and per player.
1. Check the forums
2. Check the common solutions
3. Post a dxdiag with your thread
Guide
4. Post the required information with your thread
help.sega.com/home
If you are having a CTD issue please attach a copy of your .mdmp file to your thread. (Please DO NOT RENAME THIS FILE)
To do so:
• The file we need is located by default here on your PC:
- C:\Program Files (x86)\Steam\steamapps\common\Total War Rome II
- It is a .mdmp file.[/SIZE]
• You should have one of those each time a crash happens. (Please send the newest one.)
• You will need to put them as .zip files to upload them on the forums
(NB. Crash Dump File - usually called "rome2_[Build.Number]_crash_[date][random]")
No sé si te servirá de algo...