As an administrator I want to get a list of which users are assigned to a project role. It's strange that JIRA doesn't provide this information.
I found this article https://confluence.atlassian.com/display/JIRAKB/How+to+get+a+list+of+users+assigned+to+project+roles+for+your+project but I want this information to be available on the UI.

I want to evaluate project-roles and users also in the case of nested groups.

Workaround

As a workaround, you can use several REST calls to get this data:

• Getting all Project roles currently associated in the defined Projects by projectkey: /rest/api/3/project/(projectIdOrKey)/role
  • eg. https://host.atlassian.net/rest/api/3/project/SCRUM/role
• Getting all members/users in the Project that are part of the defined Project role (project role id found in previous call): /rest/api/3/project/(projectIdOrKey)/role/(id)
  • eg. https://host.atlassian.net/rest/api/3/project/SCRUM/role/10211
• Getting user information that includes active, groups and email: /rest/api/3/user
  • https://host.atlassian.net/rest/api/3/user?accountId=(acountId)&expand=groups