You know, there is nothing like actually trying it to get you all the little details of what can go wrong... or at least, what must be accounted for.
In general, a file would take care of this, but alas, we do not (yet) have a "file feature".
The problem is in a round being tangent to a round and interrupted. I went through a manual process of getting the strong rib and still merging a tangent round to the cylindrical surface. This can be done but not directly with the round feature as it always want to step the round on the cylinder end.
Have a look at the attached file to see how this is made (Creo 2.0 M040 full version).
If you switch this to analysis surface, you can see how this merged. For a casting, this is more than sufficient.
However, a variable round can merge the end if it finishes at the same radius as the end of the cylinder.
(See prt0524a.prt).
When these details are critical, this requires some comprehensive crafting geometry in Creo.