Rome gained power because they were very wealthy. They had to trade a lot of beef, corn, glassware, iron, leather, marble and more for money. Rome controlled most of the areas around the Mediterranean Sea. They gradually conquered all enemies they encountered and gained control of Italy. Rome was at it's largest size in 117 A.D.
The Plebeians wanted more power for themselves. Most led riots to the senate and even threatened to set up their own city. In 366 B.C. a plebeian council was established. All decisions of the Plebeian council were made into laws. The Patricians eventually had to pay the Plebeians so they could live a normal Plebeian Life.
Augustus Caeser told the Romans that he was the only one who could save Rome during the crisis of Rome when it departed from being a Republic. The Romans beleived him. he started off as the first emperior of Rome in 27 B.C.E. Augustus was in the position of taking over after the Republic norms had been breaking down for more than a century. Augustus Caeser's great uncle was brutitly murdered by the senators killed him.