ASP.NET Identity 2.0 UserManager.FindByIdAsyc not returning Roles - asp.net

Question

I am building a website using ASP.NET MVC v5.2, Entity Framework v6.0 (Code First) and Identity 2.0.
I have the following code in my UserAdmin controller:
// GET: /UserAdmin/Details/5
public async Task<ActionResult> Details(string id)
{
if (id == null)
{
return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
}
var user = await UserManager.FindByIdAsync(id);
return View(user);
}
My problem is that while I can populate a user's roles with the UserManager, it is not picking up the roles associated with that user when using the FindByIdAsync method.
Here is data from the IdentityUserRole table which shows for the highlighted user assigned to two roles:
Here is the debug info showing the same user as above but the Roles count is zero:
Why are the roles for this user not being returned?
Edit #1
I am not using the default implementations for UserManager.
My ApplicationUser extends IdentityUser to allow me to add custom properties. My ApplicationDbContext extends IdentityDbContext.
Here's where I set up my primary keys for Identity using Fluent API:
modelBuilder.Entity<IdentityUserLogin>().HasKey<string>(l => l.UserId);
modelBuilder.Entity<IdentityRole>().HasKey<string>(r => r.Id);
modelBuilder.Entity<IdentityUserRole>().HasKey(r => new { r.RoleId, r.UserId });

Answer 1

As you are extending the IdentityDbContext and IdentityUser, you don't need to define your relationships for Logins, Roles and UserRoles as they are already defined in the base classes. You need to remove the lines like modelBuilder.Entity<IdentityUserRole>().HasKey(r => new { r.RoleId, r.UserId }); as they are taken care of.
As for not using the default UserManager There is a possibility here I see based on the code you have provided.
The default implementation for UserManager takes an IUserStore<TUser> as a parameter in it's constructor. If you are using (or deriving from) the UserStore<TUser> implementation in the Microsoft.AspNet.Identity.EntityFramework Library, the things like Roles, Claims and Logins are being included in the queries being made to the database. If you are creating your own class implementing IUserStore<TUser> then you will need to include the related data yourself. an example is shown below.
public class ApplicationUser : IdentityUser
{
//Add your Custom Properties here..
}
public class ApplicationDbContext : IdentityDbContext<ApplicationUser>
{
//Add your Custom Properties here..
}
public class ApplicationUserStore : IUserStore<ApplicationUser>
{
private readonly ApplicationDbContext _context;
public ApplicationUserStore(ApplicationDbContext context)
{
_context = context;
}
public async Task<ApplicationUser> FindByIdAsync(string userName)
{
return await _context.Users.Include(x => x.Roles).FirstOrDefaultAsync(n => n.UserName == userName);
}
}