Unit formations

[roman_glory]

Well, i would say that my best tactic with the romans is:
6xhastati
6xprinceps
5xtriarii
1xfm
2xroman cavalry(dont remember the name) or equites extraordinari
triarii on front, right wing with princeps, left wing with hastati and on the back the cavalry.
i put the wings oblicuous, so, they cant flank me, and then i start pushing them with hastati and princeps and make them too close, so i finish them with my cavalry
And if i'm overwhelmed by the number of enemies i usually use the famous triangle formation with the triarii in the front line or where the fight would be more complicated, a couple of hastati and princeps closing the triangle and some troops inside so they can push when necessary,with my cavalry outside, ready for smashing the enemy backs or hunt down the missile troops :)