SimpleMembership MVC 4 get data from UserProfile having role in webpages_Roles

I have the following code. But there must be a more database efficient way to do this, because, correct me if Im wrong the number of database queries is (1 + (qty of users with admin role))

With a new MVC 4 project the membership defaults are the tables UserProfile, webpages_Roles and webpages_UsersInRoles. I see lots of built in methods for Roles.Get*. If I want to avoid writing code like what I have below do I need to explicitly create a model for webpages_Roles and webpages_UsersInRoles as well as all the code first properties? Getting just the username from Roles.Get* doesnt suffice, I need the full UserProfile.

FYI the "UserRole" object below is just an enum

public ActionResult Admins()
    {
        var dbContext = new UsersContext();
        var usernames = Roles.GetUsersInRole(UserRole.SiteAdministrator.ToString());
        var adminUsers = new List<UserProfile>();
        foreach (string username in usernames)
        {
            var adminUser = dbContext.UserProfiles.FirstOrDefault(u => u.UserName.ToLower() == username);
            adminUser.Roles.Add(UserRole.SiteAdministrator);
            adminUsers.Add(adminUser);
        }

        return View(adminUsers);
    }