And yet another thing that's difficult for filleting is when you try to target only a portion of some set of sharp edges, making the fillet engine try to sort of simultaneously smooth some areas yet then collide into a sharp adajcent area.

Here's an example - here I've put in a surface/surface fillet in this spot:




If you then want the fillet to suddenly stop, it basically means there wants to be a hole created like this:




I also wasn't quite sure what you considered to be "roof-top-edge" - is it this:



Or is it this? :




Either one is probably going to have a lot of difficulties with filleting, it may be better to do an alternate type of rounding which is to slice away some area and use Construct > Blend to put in some smooth connecting surfaces rather than actual fillets.

I'm not entirely sure yet though - I'm not even quite sure what edges you want to smooth quite yet.

- Michael