"It is a room."
Translation:Det er et rum.
The difference between rum and værelse is that a rum can be any room, e.g. a conference room, a storage room, ie. any place enclosed by four walls inside a building. Værelse is more specific and refers to a room intended for people living there.
Since we do not have any context, both translations should be correct. Although, because of that, I guessed they were looking for rum rather than værelse.