Rogue Stone is for the door in the Bridge District, Tricky. This thing here is one of the many "nothing to see here, move along" points that are found in ridiculous places, such as "unfinished stairs" in a beholder lair or the friggin' Tree of Life
, or a magically fastened door 'leading to an empty storage room' in the Planar Sphere - I always wondered how can we tell it's just an empty storage, is there a visor in the door? To check up on crates?
An educated guess on my part is that when the developers created their cities and areas they used the same models for several places in order to save time. As such, for many of those houses etc there really was no intention of adding anything extra, and a room that's been created just for the sake of creating a room isn't really all that funny to explore, 'twould, again, also take up precious development time.
As for the Tree of Life etc, I really don't know, but I'm guessing they either had no time or they had problems with some aspects of the infinity engine (but you'd really have to ask a modder or game developer about that, I can't say!). We already know that many things in the final game were cut due to development deadline - 'Tis definately not an easy job to make a good game, and since BG2 is as old as it is that could've also meant that they were using less optimal solutions than we see today.
I guess there is little left to be discovered in this game.
Hehe, aye, true dat!