Much like the Black Legend, the Romans have been shown as a hegemonistic people in many depictions of History, most notably in The Bible.
The Romans were under many different Emperors and sought to conquer the world. They wanted to rule Britain and expand their rule far beyond the ancient Egyptians. They had horrific methods of killing their enemies, the most famous of course is crucifixion.
The Romans were also bloodthirsty and liked wars. Their nobility also practised the arts of incest, believing their status to be divine and believing they had the right of incest.
The Romans appear notably in the New Testament, having conquered Israel in 63 BC and having been planning their rule for quite some time ever since 53 BC. By the year 28 AD, the Romans were supremely dominant in Israel and much of the Middle East.
Much of Roman culture was linked to business, trade and commerce - much of these are now seen as the root of all evil today. The Romans were all about money and climbing the social ladder.
Also, the Romans are seen as evil because they did not recognize Jesus as divine and rejected him completely with only 2 casual mentions of him in the Bible. Even after crucifying him they did not see him as special.