How and when did the Romans form a republic centered in Rome, and what was the structure of this Roman governm

Question

How and when did the Romans form a republic centered in Rome, and what was the structure of this Roman government?

Answer 1

In 510 BC Rome witnessed a revolt against the rule of Etruscan kings.
The traditional story goes as follows;
Sextus, the son of king Tarquinius Superbus raped the wife of a nobleman, Tarquinius Collatinus. Was king Tarquinius' rule already deeply unpopular with the people, this rape was too great an offence to be tolerated by the Roman nobles. Lead by L. Iunius Brutus, they rose in revolt against the king.
Sextus fled to Gabii but was killed. Meanwhile the King with his two brothers escaped to Caere. Aided by the city of Veii king Tarquinius (or Tarquin as he is called in English) fought a battle against his rebellious subjects, but failed to win back his city.

The rebellion against Tarquinius failed to achieve final independence for Rome, but it should be the birth of the Roman republic. It was after this revolt, that the senate handed power to two consuls, although at first they were called praetors (a title which later should come to be the name of a different office of the republic). These consuls each held power for one year, in which they ruled much like joint kings of Rome.
What also needs to be kept in mind is that this rebellion was indeed a revolt by the aristocracy of Rome. Rome was never a democracy as we would understand it today, nor as the Greeks understood it. In the early days of the Roman republic all power would reside in the hands of the Roman aristocracy, the so-called patricians ( patricii).

Answer 2

Your question is somewhat tautologous for had they not formed their government centred on Rome they would not have been Romans. They kicked out the last King Tarquinius Superbus in 510BC and settled on a republican form of Government where the controlling body was the Senate made up of Patricians. The King's place was taken by two Consuls who held office for one year only. each was able to veto the actions of the other - so no one man could obtain absolute power. Later other officers were appointed, taking some of those Consuls' powers - the praetor who exercised judicial powers and the censor who dealt with the census.