This belongs here:

If you play as the Roman: Julii family, send a spy into Gaul territory. Let one of their cities grow to Minor City (level 3). Check if they have a Sacred Circle to Epona, (the horse god). Take the city. Grow to 12000 ASAP.

Wait for a 'your roman people have embraced Epona as their god'. This happens if you leave the temple alone long enough (dont destroy it, repair it if damaged).

You can now build the Awesome temple of Epona and the Pantheon to Epona, giving your legionary cohorts 4 xp (1 silver), or 5 xp (2 silver) as 'raw' recruits!

I did a search and havent found this tip anywhere so here you go. Added to the Julii walkthrough as well. (and on the org)