Personally I think there should be a better way of rotating buildings than just a 4-direction option for building rotations. Since roads have much more variation in directions they can face, buildings should be able to follow the roads in more than 4 ways of rotation. For instance, if I were to make a road face vertically down, currently I would have to place a building that won’t directly align to the road I intend to build it on.
Having atleast a 8-direction rotational option for buildings, or atleast have the same amount of directions as the roads can be build as, would grant a better and more variable in city designs. Though this may create some difficulties when using the “flatten terrain” tool with the directions, but I think it should be fairly possible as the map generates in various of angles and directions.