Originally, Rosetta Nebula had four systems. The missing one, called Iota Urania, can be found in game files of Mass Effect 2 and Mass Effect 3. This system had five planets, respectively called Walden, Erewhon, Mizora, Pala and Cascadia.
After completion of N7: Archeological Dig Site, a news report can be heard on the Citadel regarding the events that took place during the assignment. In it, the Rosetta Nebula is referred to as "Aeia Cluster".