Yeah I serve somebody, but that isn't equivalent to saying that I'm serving a god(at least not the way I would define god).

And the roman didn't kill god. They killed jesus, some normal guy who managed to create a big audience. Big enough to pose a threat for the roman culture.
By that time the writings about jesus didn't exist.
The new testament was actually written over a century after his death, and most likely parts were adapted to fit the spiritual needs of the audience.