You can use a 1-meter floor or wall to snap roof tiles to the center of the previous roofing layer. Here's my worst looking circular roof. I don't think I will use 45 degree roofing for circles anymore. https://steamcommunity.com/sharedfiles/filedetails/?id=2649688572
Build the 2-meter sections straight up and build the 4-meter sections up until they overlap without gaps with the 2-meter section, then use the 1-meter floor or wall to shorten them to 2-meter sections as well, removing sections from the next layer as the sections start to overlap.