That changes nothing about what I said.
Atlantis is still widely known for being Greek mythology not Roman, and even within the mythology Atlantis sunk long before the Romans conquered the Greeks.
But regardless this is irrelevant because Namor's name doesn't have this deep meaning in it that you're trying to assign to it, Marvel themselves quite literally say the process of picking Namor's name was writing noble sounding words backwards and picking the one they liked the best.