As I've recently been refamiliarizing myself with Romulan history and culture- particularly the activities of the Tal Shiar and its operatives- I've endeavored to learn more about the Romulans of the "Mirror Universe," only to discover that information on this subject is extremely limited. The information I've been able to piece together suggests that the Romulans of this universe were members of a Romulan Republic, as opposed to the Romulan Star Empire featured in our universe. Whether this speaks to a more benign people than those previously featured in Star Trek is difficult to determine: Benjamin Sisko spoke of meeting with Romulan representatives near the conclusion of "Through the Looking Glass," though this was likely a fabrication designed to hide his return to Deep Space 9.
Without divulging important spoiler information from various novels, I am aware of other possible outcomes for the Romulan people, though one such scenario would preclude the possibility of Romulus aiding the Terrans in their fight against the Alliance, as well as from having any political standing at all.
Without divulging important spoiler information from various novels, I am aware of other possible outcomes for the Romulan people, though one such scenario would preclude the possibility of Romulus aiding the Terrans in their fight against the Alliance, as well as from having any political standing at all.