As its been a long long time since I played the mod (too busy testing) I really cannot help you with how to max out provinces. Especially since I never play as Rome
But you might be able to find some good guides here -->
http://www.twcenter.net/forums/forum...ay-Discussions
The only advice I can give is this. Make good use of dignitaries (governors) and champions. Dignitaries must be deployed in a province which will add to your income and through different skills (as he gets experience) can be used to further increase your income. Some skills will add to farming other to industry meaning that you can pick different skills for different dignitaries depending on what region he is deployed in.
Champions are good for reducing army upkeep

Its not much but they can both add a little to your overall income.