Admirals are the Flag Officers of the Romulan Imperial Fleet. They command large military areas of the Empire, or Armadas of more than 4 ships. Their, are around 75 Admirals, but the exact figure is unknown.
A Note on Rank Insignia
Not all members of the Romulan Fleet wear rank insignia. The actual decision is made by the local commanding officer. If no rank insignia is to be worn, each crewmember is to familiarize himself with all superior officers he is likely to encounter. A point of Romulan protocol is that if you are uncertain if another person outranks you, assume so.
Their are no Enlisted ranks in the Romulan Fleet
Admiral
Admirals are the Flag Officers of the Romulan Imperial Fleet. They command large military areas of the Empire, or Armadas of more than 4 ships. Their, are around 75 Admirals, but the exact figure is unknown.
Commander
Commanders are roughly equivalent to the Federation rank of Captain. Commanders command Imperial Warbirds or large stations and garrisons
Subcommander
Subcommanders are roughly equivalent in rank to a Federation Commander. Subcommanders are senior officers on ships or stations, and are almost always "fast track" types who will be promoted to Commander.
Centurion
Centurion are roughly equivalent to the Federation rank of Lieutenant. Centurions are the backbone of the Romulan Fleet. As much as half of the Romulan Imperial Fleet are of Centurion rank. Centurions fulfill most tasks in the fleet.
Lieutenant
Lieutenant are roughly equivalent to the Federation rank of Lieutenant Junior Grade. Lieutenants are junior officers with usually less than 4 years of service. Most Imperial Pilots (Warbird and Interceptor) are of Lieutenant Rank.
Sublieutenant
Sublieutenants are roughly equivalent to the Federation rank of Ensign. Sublieutenants are junior officers usually less than 1 Romulan year out of the Imperial Academy. They always act as an assistant or relief crewman to some superior officer.