I'm still a Roassal newbie but there is an example that might be a good starting point:
exampleConditionalLayout
| b |
b := RTMondrian new.
b shape rectangle
fillColor: Color white;
borderColor: Color lightGray;
withTextAbove: #name.
b nodes: Collection withAllSubclasses forEach: [ :cls |
b nodes: cls rtmethods.
b edges connectToAll: #dependentMethods.
b layout
ifElement: #isConnected then: RTTreeLayout new;
else: RTGridLayout new.
].
b edges connectFrom: #superclass.
b layout tree.
b build.
^ b view