Update

Controllers/IdentityController.cs

@@ -22,7 +22,7 @@ namespace PSTW_CentralSystem.Controllers
         public async Task<IActionResult> RoleAssignment()
         {
             var thisUser = await _userManager.GetUserAsync(User);
-            return View();
+            return View(thisUser.Id);
         }
     }
 

Views/Identity/RoleAssignment.cshtml

@@ -4,11 +4,13 @@
 @{
     ViewData["Title"] = "Role Assignment";
     Layout = "~/Views/Shared/_Layout.cshtml";
+    int userId = ViewBag.UserId;
 }
 
 <p>
     @* <a asp-action="UserCreate">Create New</a> *@
 </p>
+@userId;
 <div id="app">
     <div class="row">
         <div class="col-md-12 col-lg-12">