How did Rome develop the idea of the separation of powers?

Answer 1

They most certainly did not develop any idea of 'separation of powers'. Quite the contrary, the Greek and Roman approach regarded law/law courts, and religion as integrated elements of politics. Both were used to control the people and to control political activity. Roman life was controlled by religious custom and practice, and the aristocratic control of law and the courts, and the priesthods made it all stick. If a vote in the assembly was likely to go against you, you got an augur to spot an omen and declare the day to be a 'no business' day. An endless series of control techniques. An example: during Julius Caesar's first consulship, his co-consul Bibulus made a nusience of himself by interrupting Caesar's legislative programme with legal obstructions. Caesar had him beaten up by a gang of thugs, so he stayed at home, spent the rest of the year as an augur declaring 'no business' days which Caesar flouted and so accumulated a list of serious prosecutable crimes. After his consulship Caesar kept a magistracy as proconsul in Gaul and so retained immunity from prosecution, so Bibulus waited. When eventually his two five year terms had run out and the Senate refused to extend in order to bring him down, Caesar knew Bibulus was waiting, that he was done for, and therefore did not disband his legions as required on the Rubicon River, but led them to Rome and retained his immunity only by force of arms.