One could argue that Romulan worlds go unmentioned because the Star Empire is a closed state. Our heroes clearly lack access and perhaps also knowledge. In contrast, we learned of Cardassian worlds chiefly in episodes where our heroes traveled in Cardassian space, such as in "Return to Grace"...
And let's not forget that everything between Romulus and the Hobus supernova is toast as well.
...Although this could quite possibly only include one planet - the one whose orbit lies between Romulus and her homestar, as shown in ST:NEM.
That is, assuming that the wave from the unnamed
supernova propagated at the sublight velocities we saw when it hit Romulus, it must
have originated at the homestar and not at any neighboring star.