Roller For Sliding Glass Door

Hi im trying to Find this Roller, Either Replace it with a New One or Fix Somehow, The Wheel Itself seems fine, its just wont stay in place like the other and im really not sure on how to go about it, the top screw does nothing ( to my knowledge ). I even tried to Unscrew the other side but that wont budge the roller out either. Please Help... The Sticker on the door frame says the following (Norandex fixed Picture Product series 435/436. 437/438 Size 94x60 Product Control # 96-0709-30 Design pressure 45 Test Glass 1/8", 3/16" 1/14" 1/14" temp) Not Sure if this relates to the Frame itself or the Doors Too....