Rome's death was a bit unusual for a nation, possibly because he was a big empire rather than a small country.
He had always gotten sick-like due to the constant conflicts which may or may not have affected the empire in a large way. But his death was not a slow, painful sickness.
The only thing that happened to him was his immortality faded and he began to rapidly age. Although, before he could even die of that, he was stabbed, beaten, and burned to death by protestors.