Most Roman mythology is based on/stolen from the older Greek Myths. The Greek and Roman Gods and Goddess are basely the same beings with different names
Bacchus: God of Wine. Greek Version Dionysus
Ceres: Goddess of Agriculture. Greek Verison Dimeter
Diana: Goddess of Hunt. Greek Verison Artemis
Mercury: Messenger of the Gods and Guilder of Mankind Greek Version Hermes
Neptune: God of the Sea. Greek Version Poseidon
Pluto: God of the Underworld. Greek Version Hades
Persephone: Daughter of Ceres' daughter stolen by Pluto to become his Queen. Often associated with Fall and Winter Greek Version Persephone
Vesta: Goddess of the Home and Family. Greek Verson Hesta
Atlantis: The most advance city in Ancient times that sank to the bottom of the Seas
Phlegethon: One of the seven rivers found in the Underworld. Known as the River of Fire
The Underworld: The realm of the Dead.
Tartarus: The deepest part of the Underworld. Home to the Titans, the evilest of people and the Gods personal jail
Cockatrice: A giant fire breath land bird similar to an emu
Kraken: A giant sea monster imprison by Neptune slayed by Peruses
Scylla: A fool creature with a woman's upper body, a torso made up of multiple heads (usually dogs), and lower body of a squid
Charybdis: A monsterous whirlpool with teeth at it center
Tityo: A titan whose chain to the floor of the Underworld. Cursed to be feed upon by the Furies each day. At night he is healed to repeat the cycle the next day. Similar to the Greek Titan Prometheus
The Trojan Horse: One of the few truly original tale in Roman Mythology. A 25-foot-tall wooden horse the Roman thought the Gods and Goddess offered them as a sign of victory of the Greeks during there year war. The Romans took the Horse to Troy, their great city of defense. That night as the Romans slept the Horse true purpose was revealed. It was a trap built by the Greeks to hide their soldiers in. With the fall of Troy, the Greek won the war.
Argonauts: A group of heroes who sailed with Jason to gain the Golden Fleece. They encounter many creatures such as the Harpies, Sirens, Scylla, and Charybdis and other threats over their four month journey