Both the Romans and the Greeks significant contributed towards the development of Modern Europe and Western Civilization as a whole.
The Greeks preceded the Romans by a thousand years and were a major power spanning Europe and Asia. They were able to develop a system of democracy by limiting the powers of the King and building a senate where ministers and lords would debate over laws.
They also developed a system of speedy trials which resembles the 7th Amendment of the United States Constitution.
The Romans were able to further develop this system into a mode codified law. Rules, regulations and taxes were modernized and standardized. An assembly was developed which is a directly related to the development of modern representative democracy in the United Kingdom.