Answer

In principle, it is forbidden to benefit from it. True, some have permitted it when no tangible object was created there, but that is strained. Simply speaking, it is similar to a lamp that was lit, from which it is forbidden to benefit.
However, someone who does not believe may possibly have the status of an inadvertent transgressor or someone under compulsion, and then there are some halakhic decisors (a minority view) who permitted benefiting from his labor on the Sabbath.
In any case, if he did this not with you in mind, you are not required to give up using the room if you had planned to use it. Certainly if this is your room.