New security role for project managers

Hi all,

I would like to create security roles in Project Management module ( in a multi- company  business)   but I need to make sure that I'm doing it right:

1. How can I create a Role where  a Project manager in a specific department can see all projects in that department? maybe adding a record level security on a specific financial dimension?

2. How can I have a role where only Project managers will see all projects? Not the project team members.

3. Also a role in which the head of the department will see all projects.