What was religion in ancient Rome

Religio Romana

The Religio Romana (literally, the "Roman Religion") constituted the major religion of the city in antiquity. The first gods held sacred by the Romans were Jupiter, the highest, and Mars, the god of war, and father of Rome's twin founders, Romulus and Remus, according to tradition.

Explanation:

The official Roman religion was the worship of a large group of Greco Roman gods such a Jupiter, Juno, Minerva and Mars. A Roman priest was responsible for the proper ritual worship to the gods. The Romans were tolerant of other peoples' gods, allowing natives in their provinces to worship whatever gods they chose :)

Hope this helps <3