Exemplo de uso de roles através das Claims

ClaimsController.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Security.Claims;
using System.Web;
using System.Web.Mvc;
using Microsoft.AspNet.Identity;
using Microsoft.Owin;
using Microsoft.Owin.Security;

namespace ClaimsLogin.Controllers
{
    public class HomeController : Controller
    {
        public ActionResult Index()
        {
            return View();
        }

        /// <summary>
        /// Exemplo para destruir a sessão do usuário
        /// </summary>
        /// <returns></returns>
        public ActionResult Sair()
        {
            var ctx = Request.GetOwinContext();
            var authenticationManager = ctx.Authentication;
            authenticationManager.SignOut();
            return RedirectToAction("Index");
        }

        /// <summary>
        /// Loga no sistema, no exemplo uso o SignIn e adiciona claim do tipo Role
        /// </summary>
        /// <returns></returns>
        public ActionResult Entrar()
        {
            var claims = new List<Claim>
            {
                new Claim(ClaimTypes.Name, "Cleyton"),
                new Claim(ClaimTypes.Email, "cleyton@email.com"),
                new Claim(ClaimTypes.Role, "Admin"),
                new Claim(ClaimTypes.Role, "Master"),
            };

            var identity = new ClaimsIdentity(claims, DefaultAuthenticationTypes.ApplicationCookie);


            var ctx = Request.GetOwinContext();
            var authenticationManager = ctx.Authentication;
            authenticationManager.SignIn(new AuthenticationProperties { IsPersistent = false }, identity);

            return RedirectToAction("Index");
        }


        /// <summary>
        /// Exibe os dados do usuario, para usuarios logados
        /// </summary>
        /// <returns></returns>
        [Authorize]
        public String Dados()
        {
            OwinContext ctx = (OwinContext)Request.GetOwinContext();
            ClaimsPrincipal user = ctx.Authentication.User;
            //var admin = user.IsInRole("Admin");
            //IEnumerable<Claim> claims = user.Claims;

            return string.Format("Nome: {0} - É admin: {1} - É master: {2}", user.FindFirst(ClaimTypes.Name).Value, user.IsInRole("Admin"), user.IsInRole("Master"));

        }

        /// <summary>
        /// Somente usuarios com a claim Admin
        /// </summary>
        /// <returns></returns>
        [Authorize(Roles = "Admin")]
        public String SoAdmin()
        {
            return "Você é um admin";
        }

        /// <summary>
        /// Somente usuarios com a claim User. Neste exemplo ele sera redirecionado para o login
        /// </summary>
        /// <returns></returns>
        [Authorize(Roles = "User")]
        public String SoUser()
        {
            return "Você é um user";
        }
    }
}

Install-Package Microsoft.Owin.Security.Cookies

Install-Package Microsoft.AspNet.Identity.Core

Install-Package Microsoft.AspNet.Identity.Owin

Install-Package Microsoft.Owin.Host.SystemWeb

Update-Package Newtonsoft.Json