I would recommend the training of a large number of warbands (8 - 10). Walk them close to the German battleline before charging them all into the fray with warcry on. I suggestwarbands as they are better at holding down the enemy infantry that swordsmen.
While the infantries are all engaged send a few sizeable units of cavalry (the heavier the better, but even standard barbarian cavalry will do) into the backs of the German battleline. Spear warbands rout very quickly if flanked.... If the first charge is not successful in causing a rout, pull them out and charge them again.
OR
If you have skirmisher superiority, position them all at the extreme side of your warbands, and order them to take up position to the left of the German infantry line. Send the cavalry around the right side, and engage the infantry with the warbands (warcry first).
Then send in the cavalry into the back/side of the German infantry as above, while they are held down by the warbands. While the German infantry is engaging all of this use your skirmishers to start throwing javelins into the Germans right wing of infantry, causing additional casulties.
Wherever possible, try to kill the general unit first - if the chance arises use the cavalry wing to isolate and kill the general (if he's not wedged in the middle of the body of the army).
As for the pressing the Romans - I'd go with a mixtue of many swordsmen/chosen swordsmen (on warcry) and skirmishers/Foresters. I actually often include a couple of units of peasants aswell. I use them to run up and take the full brunt of the Roman Infantry javelins before they charge.... that way I don't lose desent troops. Also include some light cavalry to chase and kill routers, and for hitting their general, if they leave him any way exposed.
Also - spy on them often, that way you can deploy an army more likely to emerge victorious.
[This message has been edited by Smackus Maximus (edited 06-06-2008 @ 05:38 AM).]