Jupiter
Known as the “father of men and gods” (both ceremonially and literally, since he sired numerous children with numerous women), Jupiter was originally an Italian sky god whose name was etymologically connected with Zeus, as well as other Indo-European gods of comparative status. Jupiter was “Hellenized” through this association and through the dedication of temples in his honor. The most well-known temple to Jupiter stood on the Capitoline, along with a temple to Juno, his wife, and Minerva, his daughter. The Jupiter Optimus Maximus of the Capitoline temple was worshipped as the source of Roman power. Triumphal processions, which celebrated the victory of a Roman general by displaying his booty and prisoners of war, usually followed a set route from the Forum to the foot of the Capitoline, where important prisoners were executed in public (sacrificed, as it were, in honor of the Jupiter on the Capitoline). Then the procession would ascend the Capitoline and sacrifice to Jupiter in his temple.
Another important aspect of Jupiter’s power is his control over the weather, symbolized by his lightning bolt. After lightning had struck, the Romans would perform a ritual of purification which was said to have been dictated by Jupiter himself. The legend goes that the second Roman king, the great religious reformer Numa Pompilius, asked Jupiter what was required for the rite of purification. The conversation went something like this:
JUPITER: “You need a head—”
NUMA: “—of an onion—”
JUPITER: “—of a man—”
NUMA: “—his hair—”
JUPITER: “—and a life—”
NUMA: “—of a fish.”
Jupiter, perhaps amused by Numa or impressed by his resourcefulness, granted him to use these materials for the rite (an onion head, human hair, and a fish).
Juno
Juno was originally an independent Italian goddess of childbirth and marriage, unconnected with Jupiter, whose consort she eventually became under the influence of Greek mythology. She was associated with childbirth under the title of Lucina, and her association with marriage resulted in the festival of the Matronalia. It is unclear whether Juno’s image as a scheming, manipulative goddess was already in place when Greek mythology took hold of the Roman imagination (thus prompting the Romans to associate her with Hera) or that she was identified as Hera on account of her association with childbirth/marriage and was only characterized as a vindictive woman because of this identification.
Aside from her joint temple with Jupiter, Juno had another temple on the Capitoline: on the Citadel, she was worshipped as Juno Moneta. Etymologically speaking, “Moneta” (the Advisor) shares its root with the verb monere (to advise), but this was soon forgotten and a different interpretation was imposed on it: “Moneta” was later associated with “Money”, especially since Juno’s temple on the Citadel was also where the Romans minted their coins.
Minerva
Like her Greek counterpart Athena, Minerva might originally have been a war goddess, since she often appears alongside Mars at festivals. Unlike Athena, she does not seem to be a virgin goddess: Mars’ consort Nerio is often identified with Minerva.
Minerva served a more important function as the goddess of handicrafts and all activities involving mental exertion (including but not limited to craftsmen, painters, teachers, and authors). The name “Minerva” is etymologically connected with mens (mind) and memini (remembering).