Mapping FBA Roles to SharePoint Groups in SharePoint 2013

Mapping FBA Roles to SharePoint Groups in SharePoint 2013

I've already set up Membership and Role Providers in SP2013 and a custom
login page for FBA. I can login as one of my FBA-based users, so I know
the connection to the database works. However, I'm really struggling
trying to incorporate my FBA-based roles into SharePoint. How do I map
"FBARole1", for example, to the SharePoint "Owners" group for my site,
such that anyone I put into "FBARole1" will automatically be an owner of
the site?
I go into Site Settings-->Site Permissions. I click on "Grant
Permissions". It asks me to enter names, email addresses, or "Everyone".
Makes no mention of roles. I enter any of my role names and it won't
resolve it. It can find my FBA users, just not my FBA roles. I can't think
of any other place in SP to do this.
Again, this is 2013. Any help would be appreciated. Thanks!