It really depends on the shape that needs to be rounded. There are a few possibilities that come to mind:
-
Create a Sphere of approximate size, cut it in half and create a BlendSrf between the sphere edge and the surface edge. Added bonus: continuity control.
-
Draw a rounded curve from surface edge to surface edge and use Sweep1 to “rotate” it.
-
Create a Sphere of approximate size, cut it in half and use Sweep2 on the edge of the surface and the edge of the sphere with an appropriate sweeping curve.