From Star Trek Online Geekipedia
A praetor is the title given to the leader of a political body such as a senate, a minister of law or justice, or in some instances, a military commander. Most notably, the term Praetor has been continually used to denote the leader of the Romulan Senate. While this may be an elected position with the Romulan Empire, there have been several examples of individuals securing this position through assassination, as was the case with the Praetor Shinzon, a human raised as a Reman, who grabbed power in 2379. In this sense, there are intriguing similarities between the ascension of the Romulan praetors and the praetors of Earth’s ancient Roman Empire.