"Whose room is this?"
There can be many nuances of meaning to the question here depending on how one says it. Sentence structure ("subject-object") has nothing to do with the correct translation. 这房间是谁的 ? - (curious) Whose room is this? "This room is whose?" does not sound natural in this case (except if somebody already told you whose room it is and you weren't listening). 这房间是谁的 ? - (disgust) Okay, whose room is this? (It's probably a mess.) 这是谁的 房间 ? - (shocked/incredulous/other appropriate emotion) This is WHOSE room? (Perhaps followed by: What do you mean it's his/her room? You mean, you gave this room to that---/insert expletive here/) 这是谁的 房间 啊? - (emotional) Whose room IS this? It's amazing/filthy/insert other appropriate adj./