When the Romans rebelled against the last of the seven kings, Tarquin the Proud, they swore never to have another king and they turned to a system which would prevent future tyranny: a Republic. Following the expulsion of Tarquin a law was passed which forbade royalist policies or ideals to be pursued by anyone.
The love for personal freedom and the fear of an absolutist tyrant lasted well into the future, to the point that Julius Caesar was murdered by a group of republican idealists which included his own adoptive son, Brutus. The great emperor Augustus learned of this lesson and he himself achieved absolute control by showing himself, at least in propaganda, to be disinterested in personal gain and glorification and to be always ready to give up a good share of power. That way he held on to power and increased it through time by having the Senate award him one title after another. In such a way he fashioned the figure of the emperor which was to rule over Rome for the forthcoming centuries.
Later Roman emperors were not so cautious but they had learned that the Roman hate for absolutist Tyrants and Kings could be heavily diluted by softening the mind of the Plebeians with free food and circus games. Emperor Nero went as far as making extravagant donations to the poor but this turned heavily against him when the cut price food he had promised faltered.
Read on about the Senate and other bodies of Roman government.