If you're speaking of reflections on the window of things inside the room, then fabricate a shroud around the end of the cam that extends from the cam to the glass to block any and all light from hitting the glass that originates from behind the camera and in the room.
The shroud should be opaque and black inside so that only light coming directly through the window from outside will reach the cam's image sensor and nothing from inside the room.
If you're speaking of IR reflection, turn that off in the cam and use an external IR emitter, if needed.