So, using all the information you all gave, I’m giving the roof another try at the moment, with 0.08mm layers and the default 0.42 line width.
I was wondering whether the speed you use for the printer as a whole has en effect.
Apparently it does, as I started at “Normal” but noticed that spaghetti appeared as well as defects on the “tiles” of the roof itself. So I quickly switched to “Silent” and it seems this works better. Though it obviously doubles the time needed to print then thing.