This is a list of major Roman gods and their Greek counterparts:

The Romans did not have their own set of gods.  The Romans absorbed many other religions and made them their own.  The ancient gods of Rome were from the first people of Italy, the Etruscans.  Later, the Latins and Sabines had their gods absorbed into Roman beliefs.

The most influential culture to the Roman religion was the Greeks.  The Romans took Greek myth and made it their own.  As you can see, the chart at the top of the page proves that.  Even in the golden age of Rome, the Romans brought in more gods.  Roman law was simple, worship who you want as long as you worship Saturn.

Just like the Greeks, the Romans had a pantheon of 12 major gods.  These 12 gods are:  Jupiter, Juno, Minerva, Vesta, Ceres, Diana, Venus, Mars, Mercury, Neptune, Volcan, and Apollo.  The first three are the most important out of the lot.  They are the most powerful.

The Greek list is:  Zeus, Hera, Athena, Hestia, Demeter, Artemis, Aphrodite, Ares, Poseidon, Hephaestus, and Apollo.

The Romans believed that the primordial gods, meaning the gods of the gods were faceless, formless, but very very powerful.

Rome's origins are mixed with truth and myth.  The founders of Rome are Romulus and Remus.  According the Roman mythology, these two twins have favor with the gods.

During the Trojan war, there was a warrior named, Aeneaus who was a hero, meaning that he was half mortal and half godlike, and he wondered around the Mediterranean Sea after the Trojan War.  He lands on the peninsula of Italy.  Aeneaus had a son named Amulius. 

Amulius married a woman named Rhea Silvia.  However, Amulius died and his brother, Numitor took over his throne.  Rhea Silvia was banished to be a Vestial Virgin, but lost her protection.  Once she was out of the protection of the gods, the god Mars raped Rhea Silvia.

Not taking any chances, Numitor ordered the death of the baby boys, Romulus and Remus so they could not rule the kingdom.  Since the boys were Mars' children, Mars sent a wolf to watch over, protect, and raise the boys.  The rest is history.

Here are some other gods and their importance to the Romans:

Apollo:  the god of prophecy and archery.  He is also a Greek god.  At the famous Oracle of Delphi, Apollo defeated a giant serpent named Python who was sent by the ancient earth goddess Gaia.  The serpent was to protect the priestess Pythia.  Pythia was able to answer any question posed to her.

Apollo is the son of the Jupiter and goddess Latona.  His sister is Diana

Ceres:  goddess of grain and plants

Cupid:  god of love

Diana:  Sister of the god Apollo, daughter of Jupiter and Latona.  Diana belongs to an ancient trinity name up of herself, Egeria (a water nymph), and Virbius (woodland god)

Janus:  The month January is named after this god because he is the god of beginnings and endings.  Janus is one the three major gods of Rome.  In times of peace his temple is closed, but in times of war his temple is open.  Legend has it when the Gauls (a barbarian tribe) tried to invade the city of Rome, the goose that stayed in Janus' temple started to honk, alerting the Romans of the sneak attack.  They were able to fend off the Gauls.

Juno:  She is a goddess that was married to Jupiter.  Juno was impregnated by a magical flower and produced the god Mars.

Jupiter:  The sky god, king of all the gods.  He is the equivalent of the Greek god Zeus.

Mars:  Called the father of the Roman people because he raped the mother of Romulus and Remus.  Mars was produced by his mother and a magical flower.

Mercury:  messenger god, god of trade and commerce.

Minerva:  daughter of Jupiter and Juno.  Known as the goddess of 1000 works

Neptune:  Sea god, equivalent of the god Poseidon.  However, in Roman mythology, Neptune is no where near as important as Poseidon to the Greeks.

Prosempine:  Kidnapped by the god Pluto and taken to the underworld to be his wife.  She is known as the queen of the dead.

Rhea Silva:  mother of Romulus and Remus

Saturn:  ruled the earth during the lost Golden Age of the Roman gods.  He is the equivalent of the Greek god Cronus (Titan)  Saturn was defeated by his sons.  Jupiter is responsible for the death of Saturn

Venus:  Daughter of Jupiter and Dione, wife of Vulan, and mother to Cupid, Hymen, Prispus, and Aenus.

Vesta:  goddess of the hearth (home)  She is has a special cult called the Vestal Virgins.  These Roman women promised to be virgins and protect the sacred flame of Vesta.