what was the function of the Roman cavalry?

[xrubio]

But what kind of roles this cavalry played?
I mean, veteran cavalry trained in pursuit and scouting functions is really important, because it can be used to locate the enemy before battle, and destroy it in the pursuit (or avoid it if the battle turned into defeat). In general the use of cavalry against close-order formed infantry doesn't seem to be the best option in roman times, but if they are used on these stages of a campaign they can be decisive to transform a small victory on the destruction of the enemy.

Xavi