Q:

Change Diazo theme elements based on user role

Is it possible to make elements of a Diazo theme depend on the user role in Plone? For instance: I would like to offer a different header image in the theme for some specific roles, and have these change on the site as soon as the user logs in. 
This question may be related, but I would prefer to manage it only through role assignments. 

A:

This might be possible by specifying a theme parameter.  Untested, but you could define a parameter like this:
roles = python: portal_state.member().getRolesInContext(context)

or something like:
is_manager = python: 'Manager' in portal_state.member().getRolesInContext(context)

Then use that parameter in your rules.xml file.  This would switch the theming off for managers:
<notheme if="$is_manager" />

That does nothing with headers, but you should be able to extrapolate from that.

