Hey Anthony,
You can use the "Was Added to Opportunity" filter to find the role. I would use that filter and set it to "Opportunity: is any" and "Date of Activity: on or before *TODAY'S DATE*". Then, add the "Role" Contstraint. Don't worry that if you click the dropdown and no values appear. Just type in "Billing" (or however it appears in SFDC). This should get you the list you are looking for. As always, I would double check a few names to ensure.
Hope that helps!