@NemoMania - My buddy Scott Schnoll asked me to clarify a few things here... We need to remember that Edge and UM cannot be installed as part of an environment when using the /hosting switch, so that is an impact.
To extend what Scott said to me, as one of the main proponents of this "multi-role" approach, I generally don't think about UM being part of the "multi-role server". I almost always propose the UM server(s) as being separate servers from the multi-role servers. The sizing calculator does NOT take the UM role into account when you mark it as multi-role, so you need to be aware of that.
So, last note on the /hosting switch is to reiterate - /hosting doesn't support UM or Edge, so keep that in mind!
Great question, by the way. Not many people know much about the /hosting option, so thanks for asking for clarification!