Who was Dionysus' equivalent in Roman mythology? and What god is he?

Dionysus in Roman mythology was called Bacchus.

Explanation:

The Romans took over religious beliefs from the ancient Greeks, only giving their gods other names. Dionysus, the Greek god of wine and fertility, was called Bacchus by the Romans. It is a deity that is also associated with the harvest. According to Roman mythology, Bacchus was interested in wine and grapes as a boy. It was often celebrated at various parties where there were large quantities of wine.

i think its the outcome of people's preferences.

it is the dominance of   the spanish language and roman catholic region in mexico, french being the official language of several african countries, and the existence of a western-style government in south asian countries