Windows 7Backup does not support tape media as a backup media type (this is true of Windows Vista backup as well).
You are correct; Removable Storage Manager (RSM) is also no longer included in Windows 7. Microsoft has been working with backup partners and OEMs over the past five years to gradually move away from this technology.
Windows 7 backup is designed to automatically backup to a hard disk, local network share, or disc (i.e. CD/DVD). Despite not natively supporting back up to your tape media, we hope that back up to one of the supported media types is as or more convenient and cost-effective for you.