Custom Battle Armies

I have a question, I'm new at Europa Barbarorum (I have just a week with it) so, how can I play with a Roman Army (or any other faction army) in the Custom Battle, because there appears a lot of units of many places (mostly mercenaries) but none of the Roman Units, is there something I'm missing?, how do I play a Roman Army in Custom Battle? I hope someone can help me

I found this in the FAQ:

Q: In custom battles or multiplayer the unit selection is missing units.
A: All of the regionals cause a problem for the custom battle / multiplayer list. There is a special EDU for custom battles / multiplayer in the "...Rome- Total War\EB\mp custom game edu" folder. Rename your campaign EDU then place the EDU from that folder into the "...Rome - Total War\EB\Data" folder. When you want to play a campaign again, switch back to your original EDU. EB v1.1 now comes with the trivial script, which will automatically switch the files for you. To play custom battles or multiplayer battles with all of your factional units, run the "Play Multiplayer" option of the trivial script.

Apparently the Trivial Script (optional installation item) is what switches the files for you, and you have to switch them back when you want to play a campaign. Never tried it myself as I don't play custom battles.

If you are new, read the FAQ. You will find many answer there to question you don't even know you need an answer to

There should be a Play EB Multiplayer option in the EB folder. Run that and you are golden.

thank you all guys, problem solved, Sir Robin's solution hited the jackpot