My roof rubs too, but not as bad as yours. I was told the problem could be corrected by adjusting the two springs controlling the tension on one of the top bows, but that it was a big job since the mechanism is not only complicated but fixing it required a lot of dis-assembly and reassembly. However, the mechanic didn't indicate any parts were required.
Of course, this could all be wrong. I'm a foreigner living in Italy, so I don't always properly translate the language. Plus, the Italian language is sometimes not very precise, so "springs" could have very well meant "gas struts".
Anyway, I haven't tackled repairing the top myself (yet) so I don't know what lies behind the fabric, but I did install a couple of little wooden wedges on the back glass so that it will slide over the roll hoops without catching. I attached them with black duct tape, covered the rubbing surfaces with duct tape, and lubricated them with a dab of light silicone oil. I also put a small piece of tape on top the roll hoops so the silver trim is less likely to be snagged by the top. The top still rubs, but opens and closes smoothly without that horrible TWANG as the edge of the glass catches and finally springs free of the roll hoop. The problem is not fixed but the major symptom is eliminated and the likelihood of causing damage is reduced.
If you do learn more about this common problem and how to fix it, please report back.