Neptune -> Poseidon Jupiter -> Zeus - Dias
e.t.c
Although the Romans were good at incorporating foreign deities, they had their own indigenous pantheon, which followed much of the pattern common throughout the cultures that spoke Indo-European languages. When Romans recognized similar pantheons in foreign lands, they often hybridized the names and/or stories, adding/adapting them to their own. The Greeks shared a similar pantheon, and the Romans recognized this.
The Romans did not change the names of the Greek deities after adopting them. They did recognize the common ground and they extended their Roman umbrella over the Greek mythological world, understanding that they were dealing with common ground..
According to Michael Lipka, in his book about the Roman gods, there was a gradual addition of imported gods to the Roman Pantheon. Most of the gods that ended up in the Roman Pantheon were introduced in various ways, such as merchants or travelers, to people living in Rome or Roman territory. These gods then were worshipped by individuals, who then shared with their neighbors until they gained enough following to be incorporated into the Pantheon.
The Romans often renamed the gods with Latin names to officially adopt them as their own. They also often made minor changes to the stories or powers of the gods to suit their particular narrative and, again, adopt them as their own.
This meant that the gods were not just "Greek" or "Egyptian" but properly "Roman" even if there were only superficial differences between the Roman and original versions. This renaming allowed an inclusive, yet distinctly Roman pantheon. The Romans were particularly good at absorbing and including various outsiders into their cultural being, and this comes across particularly clearly with regards to religion.