please see here: http://usermanual.clarizen.com/#roles. By default, any resource assigned to a task cannot control the life cycle state or due dates - only report progress (and put notes, etc.). So setting a resource to a task should limit that. Note, however, if a user is set up as a super user ( http://usermanual.clarizen.com/#user-permissions), they have the ability to see and control items across the system. As such, it is strongly recommended to limit Super Users. Another exception is that if a resource assigned to a task is also assigned as a manager to a higher level task in the project, that user will be able to change more than just progress.
A few other resources that would help include our weekly power user / PM training session, our weekly admin training, or our daily Q&A sessions. All are free and you can register to any of them here: http://www.clarizen.com/resources/online-demo.html#second.