How so? Vulcans were founding interstellar monasteries a thousand years before ol' Julius got stabbed: plenty of safety margin there for them having been the origin of the Romulus/Remus thing. (Presumably "Romulans" would have been a thing long before they left Vulcan to found their very own star empire, having been one of the many quarreling groups on the desert world originally, and quite possibly one of those responsible for the violent colonization period that might have touched upon Earth, too.)
But "timing" is an issue where I'd hope the events mentioned in Earth legends happened much earlier than the legends themselves suggest. We need time for the actual memory ("My second cousin was one of those serving in the flying house of this Apollo, and I suppose there was some hanky-panky, because her kid is, you know, weird. Very good at healing. But there was some argument about it, and lots of gunfire with those lightning rods of theirs. The boss man really is the violent sort!") to fade into myth ("Apollo begat Asclepius and then resurrected him after Zeus had killed him"). Preferably several centuries, but quite possibly millennia.
Timo Saloniemi