Christianity has nothing to do with the Roman Empire as its genesis did not originate with the people of the empire. It was with the Jews who came out of the portion of the Middle East by Africa that Christianity was birthed into the world. In fact, the Romans persecuted the Christians for centuries, putting them to death and everything. There were tyrant Caesars such as Nero and Domitian who tried to wipe out the Christians. The Roman Empire introduced the Caesar Worship Cult which was a system in which everyone in the empire was expected to worship Caesar as a way of bringing unity to a very diverse empire. (The empire was diverse because it conquered and assimilated the people of so many different cultures and religion. By instituting Caesar worship, they hoped to unify the people under one common religion. It was blasphemy.) Anyone who did not worship Caesar was put to death. The Christian faith does not permit one to bow down to any other god, so, since they did not comply, they were killed. Christians were made the scapegoat for calamities not of their own making and likewise persecuted until death for this. This is very similar to the whole future Antichrist scenario that will come upon the world during the Great Tribulation when you read about the Beast and his side kick, False Prophet, in Revelation 13.
Continuing on about the Roman Empire, in the book of Daniel of the Bible, the Anti-Christ is shown to rise out of a future form of the Roman Empire. He is the little horn of Daniel 7:8 that comes out of the fourth beast which is Rome. The Roman Empire itself (past and future incarnation) are both depicted as one of the 7 heads of the Anti-Christ Beast in Revelation Chapters 13 and 17. These heads, in the book of Revelation, have blasphemous names as the kings of these empires took on blasphemous titles reserved only for God. (In the Bible, the king represented the Empire when said empires were depicted on beasts and statues.) On top of the rulers of these empires taking on blasphemous titles, one of the other similarities these empires shared was the subjugation and persecution of those who worshiped The Great I Am. When the RE eventually absorbed Christianity into its culture, they actually perverted it. A lot of that perversion is still around today when one compares certain "Christian" denominations with the actual doctrines of the Bible. The Romans blended Christianity with many of the pagan religions of the day.
Anyway, I can go on forever on this. True Christianity has nothing to do with any kind of Roman conspiracy. It simply about one's own personal relationship with Christ, hence the scripture says for each man to "work out his own salvation with fear and trembling" and urges us all "to study the scripture to approve ourselves righteous, rightly divining the word."
Regarding the Gilgamesh thing you brought up, that story is believed to have been written around 2,000 BC.
http://www.webpages.uidaho.edu/engl2..._gilgamesh.htm
This is around the time Abraham was believed to be born:
http://www.matthewmcgee.org/ottimlin.html If you will look at the dates on this second site, you will see how Adam and Even predate the Gilgamesh story by over a thousand years.
Here's the thing, during the time of Adam and Eve, Cain and Able, etc, there was no need to write anything down. At that time, God spoke to man directly, so there was no reason to write anything down for future generations. As a matter of fact, I believe the Son of Man would even frequent the Garden of Eden when Adam and Eve lived there. What I believe happened was things were passed down through oral tradition until it was finally codified in writing. While the written tale of Gilgamesh may predate the first biblical writings, that does not mean that Gilgamesh could not have been inspired by oral tradition concerning The Great I Am. I believe that some of what you brought up was probably inspired by prophecies given to man by God. Its no different from what happened after Christ arose from the grave and ascended into heaven. People started writing false doctrines (or mythologies) about Christ that was untrue. My belief is this was nothing new as even during the old testament days which go all the way back to Adam and Eve (which predates any of the other religions outside of the worship of The Great I Am), we likely still got mythologies inspired by God-given prophecy.
Anyway, just saying.