"The government of Rome had three main stages from the time of ROme's beginning in 753 B.C. to the fall of the Roman Empire in the fifth century A.D. The first period is known as the regal period, when Rome was governed by a monarchy. This period lasted about 250 years. Next came the Republican era. This was a time of great conflict both within and outside the empire. It was also a time of great social and political development. The last stage in government in the Roman Empire came with imperial rule. This period began when Agustus became Rome's first emperor in 27 B.C." (Politics and Government in Ancient Rome, Gedacht pg. 5)Rome started with Indo-European peoples migrating over the Alps to the warmer climate of the Italian Peninsula. The language of the Indo-Europeans soon became Latin. Around 1000 B.C. Rome only consisted of small villages, located approximately fifteen miles inland along the banks of the Tiber River. The people of the early Roman villages were a rural folk, comprised of farmers, shepherds, etcetera. It is believed that these early Romans were organized in tribes, and even had chiefs and a council of elders. Located north of the Tiber River were the Etruscans, a people whose technologies were quite developed. The Etruscans conquered and took control of the Romans, establishing a king to rule. During the total the time of Etruscan rule over Rome, there were seven Etruscan kings. (Source)
When the Etruscans had taken over Rome, the Romans are believed to had already established the social groups of plebeians and patricians. The plebeians were the common people and the patricians were the 5-10% of the population who were the aristocrats and the wealthy. The classes of Rome, in retrospect of superiority, were based on family name. Because of this Etruscan rule, the Romans derived a great amount of their civilization's practices from the Etruscans. However, the Romans grew tired of the Etruscan kings, and during the reign of the Etruscan king Tarquin in 509 B.C. a group of upperclass Romans revolted and forced Tarquin to leave Rome. As the ruling by kingship was eliminated, Rome became a republic - the Roman Republic. The most powerful patricians became the members of the Senate, with a total of three hundred members. The Senate, during the time of the Roman Republic, was the center of power in government. The Roman Republic was centralized on the Senate and the popular Assemblies. (Source 1, Source 2)
Although the Romans had a hatred for kings (because of the Etruscan kings), they established two executives in the government, called consuls. The consuls were essentially the leaders of the Senate. The power of the consuls, however, was quite limited; they were the commander-in-chiefs of the army but could not declare war, but their jobs were mainly city management, public finances, and criminal justice. The Roman Republic era was mainly a time of development, as development of written laws was established, more divisions of government (censors, Praetors, etc.), and laws for marriage. Although the republic type government was sufficient for sustaining Rome for sometime, internal conflict lead to the fall of the government. Rome went through series of war along with the inner strife, adding to the fall. (Source 1, Source 2)
After the fall of the Roman Republic the government took an imperialistic turn: dictatorship. The first Emperor of Rome was Caesar Augustus, who restored control and peace in Rome with the Pax Romana. With the Pax Romana established, Rome maintained internal peace for the next two hundred years. During the Era of the Roman Empire much territory, particularly throughout the Mediterranean region. However, after the Pax Romana, the fall of the Roman Empire was immanent. Political and Economic problems contributed to this fall, with leaders taking control and being assassinated constantly; in the following fifty years there were twenty-six leaders. (Source 1, Source 2)
Wells, Colin Michael. The Roman Empire. Fontana Publishing, 1992.
Gedacht, Daniel C. Politics and Government in Ancient Rome. New York: Rosen Publishing Group, 2004.