Great tutorial BTW, I'll jump into a proper campaign at the weekend with one of the Roman remnants to see how they play. Just finished that battle myself, very tough indeed. This is a great introduction into what high stakes battles in this game are like. Keep your main line from being surrounded - throw missle troops in the fight to delay if need be.

You want your cav to pick off things you know will rout quickly. Try not to charge spears and pikes frontally - with 4 cav units there's no excuse(surround such units and hit them from behind, when they face the rear charge, charge them in what was their front). If you weakened Roman units early on enough, you will be routing most things with a single charge. When the cav arrives, send the missile cav to smash Roman missile troops in melee, while send all the fighty cav in a single blob to systematically smash everything. Make sure to hold center - they must hold untill the cavalry hits. Prioritize weakening/breaking Roman spears. It will probably disintegrate by the time your cavalry will be in the position to hit Romans back - they are there to wear Romans down and delay them. Make sure loosely formed skirmishers soak up Roman missiles. Try to pounce and shatter Roman cav as they try to smash your missiles while they are not yet supported by the main force (peel off some good infantry to do that while your missile troppe bog down their cav with bodies). Early in the battle, put spears in ambush near one of your flank missile units.

Total war attila tutorial