Asp.Net 5 IdentityRole CreateAsync not works - asp.net

Question

I create an asp.net 5 project with visualstudio 2015 ctp.
As you know it prepares identity system. there is a method called Register at accountcontroller and when I test it it works properly but when I add the following code to it :
before adding the new code
await SignInManager.SignInAsync(user, isPersistent: false);
return RedirectToAction("Index", "Home");
after adding the new codes :
await SignInManager.SignInAsync(user, isPersistent: false);
// new lines for adding the new Role to the database
ApplicationDbContext adbc = new ApplicationDbContext();
var roleStore = new RoleStore<IdentityRole>(adbc);
var roleManager = new RoleManager<IdentityRole>(roleStore);
await roleManager.CreateAsync(new IdentityRole { Name = "Administrator" });
// end of the new lines
return RedirectToAction("Index", "Home");
but after adding this new lines the following error returns :
InvalidOperationException: A relational store has been configured without specifying either the DbConnection or connection string to use.
It seems we must initialize dbcontext for role manager at startup. the start up code already is :
public void ConfigureServices(IServiceCollection services)
{
// Add EF services to the services container.
services.AddEntityFramework(Configuration)
.AddSqlServer()
.AddDbContext<ApplicationDbContext>();
// Add Identity services to the services container.
services.AddIdentity<ApplicationUser, IdentityRole>(Configuration)
.AddEntityFrameworkStores<ApplicationDbContext>();
// Add MVC services to the services container.
services.AddMvc();
// Uncomment the following line to add Web API servcies which makes it easier to port Web API 2 controllers.
// You need to add Microsoft.AspNet.Mvc.WebApiCompatShim package to project.json
// services.AddWebApiConventions();
}
// Configure is called after ConfigureServices is called.
public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerfactory)
{
// Configure the HTTP request pipeline.
// Add the console logger.
loggerfactory.AddConsole();
// Add the following to the request pipeline only in development environment.
if (string.Equals(env.EnvironmentName, "Development", StringComparison.OrdinalIgnoreCase))
{
app.UseBrowserLink();
app.UseErrorPage(ErrorPageOptions.ShowAll);
app.UseDatabaseErrorPage(DatabaseErrorPageOptions.ShowAll);
}
else
{
// Add Error handling middleware which catches all application specific errors and
// send the request to the following path or controller action.
app.UseErrorHandler("/Home/Error");
}
// Add static files to the request pipeline.
app.UseStaticFiles();
// Add cookie-based authentication to the request pipeline.
app.UseIdentity();
// Add MVC to the request pipeline.
app.UseMvc(routes =>
{
routes.MapRoute(
name: "default",
template: "{controller}/{action}/{id?}",
defaults: new { controller = "Home", action = "Index" });
// Uncomment the following line to add a route for porting Web API 2 controllers.
// routes.MapWebApiRoute("DefaultApi", "api/{controller}/{id?}");
});
}
Any idea?