Assuming you have granted Hard booking rights for the roles, have you tried granting "Project - View Management" rights?
PPM seems to have business rules that govern the relationship between booking rights and edit or view management rights over projects.
If you have Edit rights over a project, PPM assumes you are the Project Manager and also assumes you will be Soft booking resources.
Conversely, if you have View rights over a project, PPM assumes you are a Resource Manager and assumes you have Hard booking rights over resources.
Project Edit = Soft booking
Project View = Hard booking.
Give it a try :-)