Just to round up the few remaining onscreen facts about the mysterious Romulan ship, here's what I can recall:
* Capable of accommodating at least one runabout internally ("Improbable Cause"/"The Die Is Cast") - something of a feat for the Galaxy
, as even the giant saucertop shuttlebay would have problems with doorway height. Then again, the E-D did somehow transport three runabouts ("Emissary"). The main E-D shuttlebay does have what looks like overhead doors... Whereas the Warbird has openings in the lower wing, and the ship hovers over any small craft it intends to capture ("Mind's Eye", "Improbable Cause"). Only an offscreen Probert artwork directly associates these openings with a shuttlebay function, though.
* Capable of firing photon torpedoes ("Contagion"; a ventral location is suggested by a brief blink of light).
* Capable of firing disruptors (various eps, almost invariably from the bow emitter in the middle of the deflector - but "Contagion" features a nondescript emitter in the rather unlikely location of the underside of the top hull!). The originally intended emitters, round domes scattered around the model, are never seen firing anything, and must probably now be interpreted as something else altogether.
* Bow disruptors can fire sustained or truncated beams or compact, almost spherical bolts. The latter are preferred, ever-so-slightly, in planetary bombardment in "The Die Is Cast".
* A single pilot apparently controls the movements and armaments of the ship, or at least is the only one to verbally respond to the commanding officer's orders regarding those things. Bridge crew size is less than half a dozen in all versions of the bridge set, and sometimes only the CO is seated.
* Apart from the bridge, features holding spaces for prisoners somewhere in the lower decks (as Garak and Odo escape such a facility and part ways only two decks up from the supposedly ventral shuttlebay that holds the runabout, even though Garak is heading for the bridge which supposedly is located somewhere higher up). Also features a comfortable lounge with big portholes for top-level chitchat, a separate dining hall without portholes for top officers, and at least one cargo bay.
* Possibly not equipped with holodecks, as Admiral Jarok doesn't appear to have experience of such and is impressed by a fairly basic simulation of the Valley of Chula, and the one (unreal) Romulan holodeck from "Future Imperfect" is a planetside facility.
Nothing particularly interesting there, and certainly nothing to establish one specific role or a range of roles for the vessel.