The Romans assimilated many elements of other societies into their culture, including the mythology and gods of the Greeks. This practice is called  syncretism which means the blending or fusion of religious beliefs and practices to form a new system.

Mythology of the Roman Gods and Mount Olympus - Cosmogony
The religion of the Greeks and Romans was a polytheistic religion (with many gods - Polytheism). The Greek and then the Roman priests needed a story or myth which centered around the main Gods and Goddesses answering the questions of where they came from and their relationship to each other (this is called a Cosmogony). A 'family tree' of the Roman Gods and Goddesses explained 'who was who' and what relationships they had with each other.

The Mythology surrounding the Gods on Mount Olympus
According to both Greek and Roman mythology the abode, or home, of the gods was on the summit of Mount Olympus, in Thessaly. A gate of clouds, kept by the goddesses named the Seasons, opened to permit the passage of the Celestials to earth, and to receive them on their return. The gods had their separate dwellings but all, when summoned, went to the palace of Jupiter on Mount Olympus, as did also those deities whose usual abode was the earth, the sea or the underworld.

It was also in the great hall of the palace of the Olympian king that the gods feasted each day on ambrosia and nectar, their food and drink, the latter being handed round by the Roman goddess Juventas. It was in the palace on Mount Olympus that the Roman gods and goddesses discussed the affairs of heaven and earth. As they feasted upon their nectar, Apollo, the god of music, delighted the gods with the tones of his lyre, to which the muses sang in responsive strains. When the sun was set, the gods retired to sleep in their respective dwellings on Mount Olympus, the earth, the sea or the underworld. The principal Roman divinities were the Olympic gods including Jupiter, Juno, Mars, Minerva, Neptune, Vesta, Apollo, Venus, Ceres and Diana.