Canonically, the last events in the prime timeline we know about are the Hobus Supernova and attempts to contain it, leading to Spock and Narada's displacement in time and forking the Star Trek (2009) timeline.
While not canon, Star Trek Online has an extensive back-story describing events between the Hobus Supernova (2387) and the beginning of the game (2409), including the political events in the former Romulan Star Empire. While the original "Path to 2409" link appears to no longer exist, the events it described are summarized on Memory Beta. Several different factions wind up playing a role in the game, including one led by Sela, the half-Romulan daughter of Tasha Yar.
In the Pocket timeline (also, of course, not canonical), prior to the Hobus supernova but after the Dominion War, the Romulans are part of an alliance called the Typhon Pact, which also includes the Tzenkethi Coalition, the Breen Confederacy, the Gorn Hegemony, and the Tholian Assembly. This alliance stands in opposition to the Khitomer Accord governments (primarily the Federation and the Klingon Empire).
This time line has not yet caught up with the Hobus Supernova (the most recent novels taking place, according to Memory Beta, in 2386), but already contradict Star Trek Online in one major regard (unrelated to the Romulans but still spoilerish):
Pocket's novels assume that Terok Nor, the original Deep Space 9, was destroyed by terrorist action in 2383 (the novels Plagues of Night and Raise the Dawn) and replaced by a unique Federation-designed station (as opposed to a standard starbase) shortly thereafter (Raise the Dawn and Revelations and Dust). Star Trek Online continues to assume that the original Terok Nor/DS9 is intact. It's a major venue in the game, acting as a social hub until recent game changes saw it taken over by a rogue Dominion force.