is it possible to change look of the workbench basing on user's role?
Admin creates a process definition and can edit it,
ordinary users should only be able to start process instance and see how "far" his/her reguest is. He couldn't be able to define new process or edit old ones.
Is it posibble to hide "Authoring" or other tools buttons in the main toolbar (change the workbench UI look ) basing on user role?
Sure it is possible, we have KieACL for that look here: https://github.com/droolsjbpm/jbpm-console-ng/blob/master/jbpm-console-ng-showcase/src/main/java/org/jbpm/console/ng/client/ShowcaseEntryPoint.java#L83
That's being used to define which menus can see or it will be hidden to specific roles.