I've started many campaigns as Rome and Taras is no problem.

Just send the entire Army that is near Arpi and seige immediately. I don't assault it will fall in 5 moves, sometimes Epiros lands a relief army and the garrison will always sally but these can be easily beaten in battle.

I also use that useless fleet to ferry every extra man I can to Rhegion and siege that by move 3, I detach a unit of skirmishers to block the strats of Messina and prevent those annoying Punic allies wandering into southern Italy.

By 271BC the South is secure and it's your choice to concentrate on the North or Sicily.

I've found Epiros will always make peace after Taras falls.

I'm playing on H/M.