I am in learning phase of Drupal and ofcourse the Entity API. I have created new entity named Projects. Goal is to make a project management system for software services providers. I am actually trying to figuring out the mechanism for workflow. I have a entity now. How would i let the user with role Manager add a new project and a user with role Developer can add updates to it like status, files attachment etc.

I need a basic overview so that i can use Drupal to build application rather than a content based website.

Thanks alot