HttpContext.Current.User.IsInRole("Domain\Admin Role") return false

I am trying to switch from Windows 2003/IIS 6 to Windows 2012/IIS 8. When I using Domain\Administrator to login web page, the following code can work normally.

HttpContext.Current.User.IsInRole("Domain\Admin Role"), it will return true.

However, When I using Domain\User1 to login web page, it will return false.

Any suggestion, Thanks in advance!