The Romans ARE weak when the game starts, if you use historical legions. The hastati are little more than skirmishers with a shield. The principes are really nothing special, although they excel against cavalry most infantry units will inflict heavy casualties. The triarii are amazing, but they are experienced men dressed in Greek style armour and fighting as hoplites, they're supposed to be tough. Plus, if you play historically, you should have only 2 units in your armies at MOST, and shouldn't use them unless it is absolutely necessary. As for the Roman cavalry, Psh... I bring them along to act as router chasers, it's all they're good for.

The reason the early Romans seem so strong is because the AI is dumb even compared to a dumb human player. To the AI, a dumb human player is what Alexander the Great was to the known world... A serious threat you're just never going to beat. Unless of course the human is playing as Hayasdan, but that's another story.

Anyhow, take a look at Carthage's starting unit roster. Libyan spearmen and Poeni hoplites... Instantly better than Rome's best troops, the Triarii. Cheap but effective light infantry in large numbers, the Iberi Caetrati (i think) very manouvreable. Light skirmisher cavalry perfect for cutting down routers before they can reform and come back, medium cavalry that trumps anything the Romans can throw at you. Elephants.... Used correctly, enough said. A general with 3 stars of command. A starting position that will never be invaded except possibly by Ptolemies around 220BC.

A navy capable of blockading the exposed Roman ports since the Romans only start off with 1 single fleet or crappy boats.

Carthage is an absolute powerhouse to be feared in comparison to Rome at the start of the game. Why do we need not fear them? Because the AI are dumb. Theie navies will never touch your ports. Their 3-star general will get himself killed charging ahead of his army. The elephants will let your skirmishers cut them down before they touch your lines. Their Poeni hoplites will split up in battle and allow themselves to be surrounded. They won't expand into Syracuse, Messana or Rhegion.

If the AI was smart, as smart as the human player or almost as smart, the Romani would be destroyed outright by Carthage.

Rome isn't overpowered, the AI is just dumb.