Power BI Embedded and RLS

My company is hoping to deploy Power BI Embedded to a platform we allow our customers to access without needed a paid Power BI account. My boss and I are database and reporting guys, not web devs, and some of the particulars are going over our heads. We'd like to employ RLS in a multi-tenant database. This seems perfectly doable, but we can't possibly designate roles to all the accounts that might access the reports. This, presumably, is where using Embedded comes in, but we still need to pass a role to Power BI to implement RLS for the users who have authenticated into our portal. I gather this is something involving tokens, but my expertise does not extend to this area. 

What information do I need to provide to our web devs to help them properly authorize our customers to view our reports and manage access to their particular data?

I realize this is a big question and I sincerely appreciate any help you can offer.