Comment 3 for bug 1278920

This issue is due to single calls triggered for each user that has a role in a project: https://github.com/openstack/horizon/blob/master/openstack_dashboard/dashboards/admin/projects/workflows.py#L209

And it can be easily addressed by fetching all roles in a project scope using just a single API call: /v3/role_assignments?scope.project.id=<project_id>. But, the /v3/role_assignments endpoint is not supported by OSC yet, therefore is not implemented at keystoneclient: https://bugs.launchpad.net/python-keystoneclient/+bug/1246310

About usability issues, maybe is better to open another bug/blueprint related just to UI usability improvement?

What do you think?