While I had a single roller on the shutter, it had a double one on the double glazing due to weight. On the shutter, the door can easily be removed, and then we unscrew and remove the lower horizontal aluminum frame for changing the rollers. On the double glass, we remove the door, place it on a support, and remove the two vertical side aluminum frames. The horizontal lower frame is usually stuck to the double glass with black rubber due to weight. If a screw gets stuck, we apply anti-rust oil and not too much force, as it may break the head of the screw. The rollers I got were unlubricated in the bearings, so I lubricated them and noticed a big difference. My old rollers were made of Teflon and had a diameter of 34 millimeters instead of 38 mm. Over time, the bearing of the old ones broke, and it made a scratching sound when sliding the door. Here, the technician provides a very good method for changing the rollers without even removing the door!
https://m.youtube.com/watch?v=Z2bm8MZiFgI