Where in Roberts Rules of Order does it state that meetings are open
to the entire public and any member taking part in a session of a body
can notify anyone and everyone about what happened during the session?

I have RR somewhere and read them, but I don't believe that they cover
this for the very specific reason that the rules deal with
parliamentary procedure  - how a meeting should be run -  which may
apply to meetings of private organizations as well as those of
political entities.  Private organizations, such as businesses and
clubs,  may define in their bylaws whether their meetings are open to
the public.  If this is not the case, the chairman at the start of the
meeting should announce that non-members are present (especially if
the press is) and may call from a motion from the floor on whether
they should be allowed to remain, or call for a motion that the
meeting be "in camera".  Here is a definition of the expression:

"meeting ? (réunion à huis clos) ? A meeting from which the public is
excluded. Committees routinely meet in this way to deal with
administrative matters and to consider draft reports; the House begins
each sitting in camera for the saying of prayers and may also deal
with housekeeping or other matters before the doors are opened. ?
Compare: secret session"
www.parl.gc.ca/information/about/process/house/glossary/glossary2004-e.htm

In this case, it is assumed that the proceedings should not be divulged.

Here is a site with Robert's Rules of Order:
http://www.rulesonline.com/