From the heavens to the underworld, the Greeks and Romans both had a vast selection of gods and goddesses to worship, but just how different were they?
We know that the roles of the deities were often shared. Zeus, or Jupiter, is a good example of these similarities. In both versions of the mythos, he was the King of the Gods, as well as ruling over sky and thunder. He was known to wield a lightning bolt and was represented by the eagle, a detail that appears in re-telling, but the Greeks also represented Zeus with the image of the bull; this does not feature in Roman history.
While these smaller differences appear throughout the descriptions of almost every deity, these are purely cosmetic alterations, most likely made to better symbolize the culture that the nation was trying to foster. To find true disparity, we must look at the context within which the gods existed.
The Roman gods were only established centuries after the Greeks had started to forge their mythos, meaning they were often improvements on the Greek gods, at least in the eyes of the Romans. They had taken what were essentially human emotions, which the Greek gods were based on, and turned them into objects of worship.
Zeus was transformed from a figure of power with fidelity issues into Jupiter, a mighty leader who helped forge the foundations on which Roman democracy and governance was created. He became a basis for the oath of office that consuls would use to complete their vows of service, as well as Jupiter serving as the sole source of true state authority.
In short, the Greeks saw their gods as a tangible, physical being that existed on a plane of beauty and greatness unachievable by humans, but their myths spoke of humans that tried. The Romans saw the gods as an idea, a nondescript source of knowledge resting in the imagination of the individual.