Rose canes do die back. Have you fed the rose? If the base is still alive it will try to send up shoots, but it will have to do it soon because it is living on its reserves.
I don't care for most knockout roses. Although they are supposed to be more carefree, I have not found that to be the case and I like the tall hybrid teas and larger flowers. The knockouts I have are short roses under three feet. The roses are nice but my ground cover rose is taller.