door rollers

hi my pella sliding doors were new in 1994 they are white wood inside probably pine they are metal outside looks like aluminum they are double pain outside and single pane inside with the window shades attached that go up and down with a light cord to raise and lower the shade is inside the glass between the outside and inside glass i need rollers for this door can you identify from my description i dont want to remove door to measure roller because of the weight right now i dont have a camera for pictures thanks if you can help