Several people seem to have the idea that Roman soldiers didn’t run into battle. Many accounts testify that they did.
It was probably a fast jog trot, keeping more or less in line. Caesar implies that this could result in some disorder, but it was worth it. The soldiers raised a loud shout, rising from a low pitch to a high pitch, as they charged. They hurled their pila while running, drew their swords, and charged home
Another misconception is that Romans fought shoulder to shoulder. They didn’t, they fought on a frontage of about a yard per man. They needed to have space to swing their swords and fight freely. There are several accounts of fighting enemies packed too closely together, which gave the Romans a great advantage.
In general I agree with most of the things @Martin_Hyde has said. This kind of fantasy match-up doesn’t really make sense. It’s based on computer gaming. In real war things never happen in isolation, or in clinically perfect circumstances, and armies have several different types of troops fighting together for a reason.