field to name relationship between two objects?

Hello,

In a CRM-like application I have two objects, one for opportunities and one for contacts, in a many-to-many relationship. The people who are recorded in the contacts object can play different roles in opportunities, for example, as an opportunity owner or as an opportunity consultant. Each contact can play only one role per opportunity, while each opportunity will have multiple contacts playing different roles. I want a field to capture that information -- in essence, to name the relationship. Then I can sort, filter, etc. by that field to, for example, show the team for a given opportunity and show which role each person played, show all the opportunities a person worked on and which role they played for each, and list by all opportunity owners or all opportunity consultants with the related opportunities. Any suggestions on how to do this?

Thank you!

Greg