This is not a feature
Pivotal Tracker is a nice tool, however it lacks verbose permission and role functionality. Currently Pivotal Tracker only defines 3 specific roles for projects which are:
- Owner
- Member
- Viewer
Account roles can be viewed here. At this time, one cannot describe what a particular role should have access to/capability to perform. For additional information on this request, you can see a discussion history of it herehere.