Its not something addressed to often in Trek, but lets not forget that this wasn't a colony, but the first world of the Romulan Empire. It had to have billions living on it. Even if they got a weeks advanced notice on it, they couldn't evacuate even a fraction of the population in time. Of course things happen in Trek all the time and we just have to accept certain things (like a shockwave moving at warp speeds to be a concern for a planet potentially light years away).
Star Trek Online is suppose to be a continuation of the existing timeline (running under the time travel theory that changing history creates an alternate timeline, so the original timeline still exists, you just can't return to it from the past anymore). So it exists in a universe where Romulus is destroyed. I don't have all the details (I'm not able to play a lot because of the computer I have) but Romulus is suffering political turmoil. Factions are fighting for dominance, the Klingons are moving to annex star systems (and the reason they haven't gone full force is the war with the Federation) and Starfleet is trying to prevent Klingon expansion while maintaining stability even if the Romulans object.
I've read that the current TNG story arc in the books may be leading towards the events before the movie (the destruction of Romulus) but I don't remember what year that is supposed to happen. I didn't think the books were at that point yet.