Below are a list of Ranks in the Star Trek Universe. You will see the Starfleet Rank and it’s Romulan Republic Equivalent
Starfleet Rank | Romulan Republic Rank
Ensign | Uhlan
Lieutenant J.G. | Sublieutenant
Lieutenant | Lieutenant
Lieutenant Commander | Centurion
Commander | Subcommander
Captain | Commander
Rear Admiral | Subadmiral
Vice Admiral | Vice Admiral
Admiral | Admiral
Fleet Admiral | Fleet Admiral