Yes, the roof panel consists of carbon fiber weave, actually it’s pieced together from scraps trimmed off the main Life Module panels during production. A visible example of the sustainable process used during production. The process was touched on during an Autoline After Hours podcast with a BMW production manager.
The body panel discussion starts around 09:35. They don’t specify how the panel is finished, just stating that it’s a “class A surface.” There’s another episode that goes into the i3 tear down performed by Munro Associates. They may have gotten into the roof panel then. I can’t recall.