The main differences between Greek and Roman mythologies are the names and descriptions of the gods and to what extent the citizens accepted the mythologies as history. Most of the Roman gods and legends were directly based on their Greek predecessors, so even though they were recorded differently, many aspects of the mythologies are similar.
Many people confuse Greek and Roman mythologies, particularly their gods, most of whom have direct counterparts in each other's culture. For example, Greece's Zeus and Rome's Jupiter both lead their pantheons; Poseidon and Neptune are each gods of the sea; Artemis and Diana are goddesses of the hunt.
There are some minor differences in characteristics, but the main differences lie in representation. The Greek histories, plays and visual representations provided much more thorough portrayals of the gods, giving them beautiful appearances and distinct personalities; the Roman gods had to perform the same functions as the Greek gods, but much more about them was left to the imagination. Of course some of the gods, particularly the minor ones, do not have a mirror in the other culture, and both cultures wrote about different mortal and demigod heroes, according to the J. Paul Getty Museum.
The origins of the Greek gods are uncertain, seeing as they predate accurate historical record, but scholars have theorized that their influence extends back to 1200 BCE. At that time, it was common for the citizens to accept mythology as factual history, rather than a set of parables and philosophies. By the time the Romans incorporated the Greek gods into their own history and religion around the second century BCE, they were more willing to see the fantastic stories as exaggerated lessons than precise historical accounts. The differences between the two mythologies seem to reflect the differences of the two cultures moreso than being distinct themselves.