China was both more technologically advanced and numerically superior to Rome. The only way they could have warred would have been if they had been in close proximity to each other, but they were literally at the opposite ends of the world.

China really had no true massive organized enemies to fight against in most of its time, so its hard to judge how they would have warred. Some interesting facts:

The Chinese had developed the crossbow and repeating crossbow (chu ko nu commonly known) by the height of the Roman empire.
The Chinese also developed a variant of the halberd (the Ji) long before they appeared in Europe, and was a common infantry weapon. In fact, they have been dated as early as the Shang era (1766BC-1050 BC).
I know this is more medieval history, but the peace time standing armies of England and France in peacetime were in the tens of thousands (40 to 50 thousands). China during the Ming Dynasty had a peacetime standing army of over 1 million

It would be interesting to see a virtual China vs. Rome battle, but that definitely would not be realistic, and in all honesty, the technological and numerical superiority would be hard to illustrate in a game.