Roman army:

1 General unit, rarely a family member (I enabled recruitable generals for all factions)
4 early legionary cohorts ( Outer provinces rarely have high level barracks to recruit regulars)
5-6 legionary cohorts (5 if I have 1st cohort) trained from high level citys to help economy
2 roman cavalry of any kind
3 archer auxillia
2 infantry auxillia for flanks
2 Heavy/regular Onagers


I group my Legionarys in a double line, alternating regs and earlys:
Spoiler Alert, click show to read: 
|reg| |early| |reg| |early| |first|
|reg| |early| |reg| |early| |reg|


I then have my archers and onagers infront set to fire at will, onagers use flame. My auxillia are on the flanks with the cavalry outside of them. When my archers start firing, I prepare to move my double line forward to keep the archers and onagers inbetween them. I set the font row to fire at will, and let the enemy charge. They usually break fast. The flanks are great because of the cav/spear combo, which also allows me to flank the enemy. My general sits behind the lines. If my front ranks retreat, my second ranks immediatly charge without throwing pilla. When one of them is wavering, I general charge while using his rally button. This is actually a historic legion...it works fantastically and is cheap to maintain. Of course it post-marian, for pre-marian I use the historical 3 lines. Also, to beat you cowardly greeks and macedonians, I throw both pilla then charge both ranks to a spot behind the hoplites, causing a few casualties but once they get in deep enough your men's spears are too long to reach me and the legionars prevail at H2H. That was defensive (which is smarter to play for this setup) For offense, I simply move to within range of onagers, unload ammo, archer range, unload ammo, the pilla range and unload both ranks' pilla before charging...no one can stop that.