Добавил контроллер для работы с ролями

webinar65/Controllers/RoleController.cs

+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Identity;
+using Microsoft.AspNetCore.Mvc;
+using webinar65.Models;
+using webinar65.ViewModels;
+
+namespace webinar65.Controllers
+{
+    public class RoleController : Controller
+    {
+        private RoleManager<IdentityRole> _roleManager;
+
+        public RoleController(RoleManager<IdentityRole> roleManager)
+        {
+            _roleManager = roleManager;
+        }
+
+        public IActionResult Index()
+        {
+            return View(_roleManager.Roles);
+        }
+
+        [HttpGet]
+        public IActionResult Create() => View();
+
+        [HttpPost]
+        public async Task<IActionResult> Create(RoleCreateViewModel model)
+        {
+            if (ModelState.IsValid)
+            {
+                var result = await _roleManager.CreateAsync(new IdentityRole(model.RoleName));
+
+                if (result.Succeeded)
+                    return RedirectToAction("Index");
+
+                foreach (var error in result.Errors)
+                {
+                    ModelState.AddModelError("", error.Description);
+                }
+            }
+
+            return View(model);
+        }
+    }
+}

webinar65/Startup.cs

@@ -61,6 +61,7 @@ namespace webinar65
             app.UseHttpsRedirection();
             app.UseStaticFiles();
             app.UseCookiePolicy();
+            app.UseAuthentication();
 
             app.UseMvc(routes =>
             {

webinar65/ViewModels/RoleCreateViewModel.cs

+using System.ComponentModel.DataAnnotations;
+
+namespace webinar65.ViewModels
+{
+    public class RoleCreateViewModel
+    {
+        [Required]
+        public string RoleName { get; set; }
+    }
+}

webinar65/ViewModels/UserCreateViewModel.cs

+using System.Collections.Generic;
+using System.ComponentModel.DataAnnotations;
+using Microsoft.AspNetCore.Identity;
+using webinar65.Models;
+
+namespace webinar65.ViewModels
+{
+    public class UserCreateViewModel
+    {
+        [Required]
+        public string Username { get; set; }
+
+        [Required]
+        public string Email { get; set; }
+
+        [Required]
+        public string Password { get; set; }
+
+        public List<IdentityRole> Roles { get; set; }
+    }
+}

webinar65/Views/Role/Create.cshtml

+@model webinar65.ViewModels.RoleCreateViewModel
+
+@{
+    ViewBag.Title = "Create Role";
+    Layout = "_Layout";
+}
+
+<h2>Create Role</h2>
+
+<div asp-validation-summary="All" class="text-danger"></div>
+
+<form asp-action="Create" method="post">
+    <div class="form-group">
+        <label asp-for="RoleName">Role Name</label>
+        <input asp-for="RoleName" class="form-control"/>
+    </div>
+
+    <button type="submit" class="btn btn-primary">Create</button>
+    <a asp-action="Index" class="btn btn-secondary">Cancel</a>
+</form>

webinar65/Views/Role/Index.cshtml

+@using Microsoft.AspNetCore.Identity
+@model IEnumerable<Microsoft.AspNetCore.Identity.IdentityRole>
+
+@{
+    ViewBag.Title = "Roles";
+    Layout = "_Layout";
+}
+
+<h2>Roles</h2>
+
+<table class="table">
+    <thead>
+    <tr>
+        <th scope="col">ID</th>
+        <th scope="col">Role name</th>
+    </tr>
+    </thead>
+    <tbody>
+    @if (!Model.Any())
+    {
+        <tr>
+            <td colspan="3" class="text-center">No Roles</td>
+        </tr>
+    }
+    else
+    {
+        foreach (IdentityRole role in Model)
+        {
+            <tr>
+                <td>@role.Id</td>
+                <td>@role.Name</td>
+            </tr>
+        }
+    }
+    </tbody>
+</table>
+
+<a asp-action="Create" class="btn btn-primary">Create</a>

webinar65/Views/Shared/_Layout.cshtml

@@ -30,6 +30,7 @@
             </div>
             <div class="navbar-collapse collapse">
                 <ul class="nav navbar-nav">
+                    <li><a asp-area="" asp-controller="Role" asp-action="Index">Roles</a></li>
                     <li><a asp-area="" asp-controller="Home" asp-action="Index">Home</a></li>
                     <li><a asp-area="" asp-controller="Home" asp-action="About">About</a></li>
                     <li><a asp-area="" asp-controller="Home" asp-action="Contact">Contact</a></li>