The ITxRobot interface exposes a Baseframe property, but it is only a getter, so you cannot change the base frame with a new frame.
What is possible to be done is to modify the location (AbsoluteLocation property) of the existing Baseframe.
Almost all parts and resources implement that ITxGeometryCreation interface, but not the compound ones. All parts and resources that can be open for modeling and under which we can add geometric entities, we also call them components (they implement also ITxComponent).
You can take a part/resource component from the selection and open it for modeling (SetModelingScope method of ITxComponent interface) and then create the sphere under it.
If you want to create a new component, then you should do it in PS (New Part/New Resource) commands under modeling menu.