From their website:
Romulan Armada is a sourcebook for Starmada: The Universal Game of Starship Combat that gives players the chance to enter the rich and vast playground of the Star Fleet Universe. This product contains all of the rules options, additions, and starship designs necessary for players to pit forces of the Romulan Star Empire against their perpetual enemies, the Star Fleet of the United Federation of Planets.
Also included is a mini-campaign allowing players to fight out the opening moves on “The Day of the Eagle”: the Romulan invasion of Federation space that brought them into The General War.
Starmada’s modular design means players can handpick from dozens of options, creating the type of game you want to play. In addition, the game’s flexible and comprehensive starship construction system lets you build your own designs to test against the best the Federation and Romulans have to offer.
Although ownership of Starmada: The Admiralty Edition Core Rulebook from Majestic Twelve Games is strongly recommended, it is not required: the essential Starmada rules are included.