How to get application roles assigned for current logged on user via C# and GraphServiceClient

Question

I have an ASP.NET 6.0 C# application which is registered in Entra ID, let us say it is called MyApp. In the Azure portal for MyApp, under App registrations, I have used Manage - App roles to define custom roles, Editor and Viewer. Then in Manage - Users and groups I have assigned users and groups to these roles.

In the application code I have a GraphServiceClient. With the following code I can get a collection of AppRoleAssignments, where gs is a GraphServiceClient object:

var approles = await gs.Me.AppRoleAssignments.Request().GetAsync();   

However these AppRoleAssignments are not the custom roles. If the user has a role assigned, there is one AppRoleAssignment that has a ResourceDisplayName of MyApp in the approles collection above, but how can I get the custom roles, Editor or Viewer, assigned to the currently logged in user?

I have looked at this sample https://github.com/Azure-Samples/active-directory-aspnetcore-webapp-openidconnect-v2/tree/master/5-WebApp-AuthZ/5-1-Roles which shows how to set an Authorize attribute using a custom role but I don't want to do that, I want code to list the custom roles in MyApp that are assigned to the current user.

Update: this is one solution

 private bool IsCurrentUserInRole(string role)
    {

      foreach (System.Security.Claims.Claim claim in User.Claims)
      {
        if (claim.Type == System.Security.Claims.ClaimTypes.Role)
        {
          if (claim.Value == role)
          {
            return true;
          }
        }
      }
      return false;
    }

I am still not sure how to do it with GraphServiceClient