The Roman republic was headed by two annually elected consuls who didn't act as executives, proposers of legislation, and commanders of the army. Later new officers of state were created. The praetor was a bit like a chief of justice and presided over civil law cases. He also had imperium, the power to command an army. The censors were responsible for the census, public morality, public works and the financing of these. They also enrolled senators. The curule aediles were responsible the maintenance of public buildings, regulating public festivals, and enforcing public order. The quaestores supervised the treasury and financial affairs of the state and the army. All officers of state were elected and acted independently within their remits. Here was no centralized administration.
There were two assemblies, the assembly of the tribes (comitia Tributa) and the assembly of the soldiers (comitia centuriata). The former elected lower officials (aediles and quaestores) and acted as court of appeal for ordinary cases. The latter could declare war, elected the higher officers of state, conferred imperium to consuls and praetors and censorial powers to censors, and acted as court of appeal for cases involving death penalty and treason. Both assemblies were presided over by the consuls of praetors.
The Romans did not elect representatives. The senate was an unelected body. It was not a legislative body and did not propose laws. It was an advisory body and could advise on legislation. It issued instructions to officers of state by decree. Originally its main membership was from former consuls, but over time other former officers of state had access to it. It became the most powerful body in the state with Rome's expansion into Italy as it was capable to organise the logistics of war and conquest.
The poor plebeians started a breakaway movement to fight for thei grievances, the abuse of defaulting debtors by rich creditors, indebtedness and land shortage for the poor. They created their own assembly, the plebeian council (concilium plebis) and leaders, the plebeian tribunes who were assisted by the plebeian aediles. The resolutions of this council (plebiscites) were not originally recognised as laws binding on all citizens (thus, including patricians), but later became laws binding on all. The plebeian tribunes became the main proposers of legislation and the plebeian council the main legislative body. Previously the consul proposed laws to the other two assemblies.
In the early republic the patricians, an aristocracy, monopolised the senate and the offices of state. The leaders of the plebeian movement, who were rich plebeians pressed for access to the offices of state and gradually were admitted to all of them. In this process a patrician-plebeian oligarchy was created. These leaders then turned their back of the poor plebeians and enjoyed power and privilege. Thus the Roman republic was an oligarchy run by the rich and powerful. However, its voting system provided an element of democracy, even though, within this system, the vote of the rich counted for more than that of the poor.
More to add on:
The Roman Republic was a democracy. Its government consisted of the Senate and four assemblies:
the Comitia Curiata
the Comitia Centuriata
the Concilium Plebis
and the Comitia Tributa
