what was the function of the Roman cavalry?

[Aryaman2]

Does it not depend on what infantry is facing the cavalry charge? Would long pikes/spears not be more effective in warding off the charge (and don't forget supporting missile fire) and causing confusion amongst the cavalry?

maybe we could say that cavalry charges are difficult in breaking heavy infantry if these are unwavering and armed with pole arms?

Certainly, pikemen blocks were less vulnerable than, say arquebussiers in skirmish, to present 2 extremes, my point is simply that even a block of pikes was not impossible to break by cavalry, and that not always would cavalry refuse contact with such a body, as has been fashionable to claim.