In my Program.cs file I added:

builder.Services.Configure<CookieAuthenticationOptions>(CookieAuthenticationDefaults.AuthenticationScheme, options =>
{
    options.AccessDeniedPath = "/access-denied";
});

I added my custom AccessDenied.razor component/page and using

@attribute [Authorize(Roles = "Admin,Standard")]

at the top of pages or the AuthorizeView tag in the pages

<CascadingAuthenticationState>
                <AuthorizeView Policy="RequireValidUser" Context="ImpersonationComponent">
                    <Authorized>
                        <Login />
                    </Authorized>
                </AuthorizeView>
            </CascadingAuthenticationState>

I was able to get role based authorization working.