Bryant's defence of the approach is interesting:
> In the Preface to my version of the Iliad, I gave very briefly my reason for preserving the names derived from the Latin, by which the deities of the Grecian mythology have hitherto been known to English readers —that is to say, Jupiter, Juno, Neptune, Pluto, Mars, Venus, and the rest, instead of Zeus, Herè, and the other names which are properly Greek. As the propriety of doing this is questioned by some persons of exact scholarship, I will state the argument a little more at large. The names I have employed have been given to the gods and goddesses of ancient Greece from the very beginnings of our language. Chaucer, Spenser, Shakespeare, Milton, and the rest, down to Proctor and Keats —a list whose chronology extends through six hundred years —have followed this usage, and we may even trace it back for centuries before either of them wrote. Our prose writers have done the same thing; the names of Latin derivation have been adopted by the earliest and latest translators of the New Testament. To each of the deities known by these names there is annexed in the mind of the English reader —and it is for the English reader that I have made this translation —a peculiar set of attributes. Speak of Juno and Diana, and the mere English reader understands you at once; but when he reads the names of Herè and Artemis, he looks into his classical dictionary. The names of Latin origin are naturalized; the others are aliens and strangers. The conjunction and itself, which has been handed down to us unchanged from our Saxon ancestors, holds not its place in our language by a firmer and more incontestable title than the names which we have hitherto given to the deities of ancient Greece. We derive this usage from the Latin authors —from Virgil, and Horace, and Ovid, and the prose writers of ancient Rome. Art as well as poetry knows these deities by the same names. We talk of the Venus de Medicis, the Venus of Milo, the Jupiter of Phidias, and never think of calling a statue of Mars a statue of Ares.
> For my part, I am satisfied with the English language as it has been handed down to us. If the lines of my translation had bristled with the names of Zeus and Herè, and Poseidon and Ares, and Artemis and Demeter, I should feel that I had departed from the immemorial usage of the English tongue, that I had introduced obscurity where the meaning should have been plain, and that I had given just cause of complaint to the readers for whom I wrote.
0: https://standardebooks.org/ebooks/homer/the-odyssey/william-...
Because this unification of the Roman and Greek gods has happened a little earlier than the time from which we begin to have preserved Latin texts and because the Greek gods came with a huge number of stories attached to them, unlike the Roman gods, which previously were mentioned mostly in rituals and prayers, we have extremely little information about the traditional Roman gods.
With the exception of Jupiter/Zeus, most of the Roman gods had been very different from the Greek gods who replaced them and it would have been interesting to know more about their original roles.
For instance the Roman Mars was extremely unlikely the Greek Ares. Mars was a beloved god, the most important protector of the Romans, who defended them against various kinds of bad things, like a COVID pandemy or climate change. He was not a god of war, even if his protector role meant that he could also help the Romans in wars. On the other hand, the Greek Ares was a god of destruction who was feared and hated. The Greeks sacrificed to him mostly to avoid his anger, but when they wanted help in war they usually turned to other gods, e.g. to Athena, which is why in the Iliad Athena gives some good beatings to Ares.