You have asked a question that identifies how crucial the setting is to the story. The rooms where the masquerade ball is set are symbolically key to understanding what is happening and going on as the revellers pass the night in diversion whilst the Red Death is laying waste to the land around the castle. Consider how the text describes their layout:
There were seven - an imperial suite. In many palaces, however, such suites form a long and straight vista, while the folding doors slide back nearly to the walls on either hand, so that the view of the whole extent is scarcely impeded... The apartments were so irregularly disposed that the vision embraced but little more than one at a time. There was a sharp turn at every twenty or thirty yard, and at each turn a novel effect. To the right and left, in the middle of each wall, a tall and narrow Gothic window looked out upon a closed corridor which pursued the windings of the suite.
It is key to note as well that the rooms run from East to West, with the final room being the black room. Note that against the Western wall of this room there is placed a giant ebony clock. Of course, as the sun rises in the East and sinks in the West, this room is symbolic of death, and thus it is entirely appropriate that the Red Death chooses to let himself be discovered in this room. Hope this helps with how crucial the setting is to this excellent story!