Usage of User.IsInRole() in a View

You could write your own extension method and use it in your code.

public static class PrincipalExtensions
{
    public static bool IsInAllRoles(this IPrincipal principal, params string[] roles)
    {
        return roles.All(r => principal.IsInRole(r));
    }

    public static bool IsInAnyRoles(this IPrincipal principal, params string[] roles)
    {
        return roles.Any(r => principal.IsInRole(r));
    }
}

Now simply you could call this extension method like this:

// user must be assign to all of the roles  
if(User.IsInAllRoles("Admin","Manager","YetOtherRole"))
{
    // do something
} 

// one of the roles sufficient
if(User.IsInAnyRoles("Admin","Manager","YetOtherRole"))
{
    // do something
} 

While you could use these extension methods in views as well but try to avoid writing your apps logic in views as much as possible since views not unit testable easily.