Rick,

Actually, if you have a several day reuse delay period defined on your tape
storage pools, you can roll back your database that many days and your tapes
are guaranteed to not have been overwritten.  All the data will still be
there because objects are just expired from the database, not physically
overwritten.  Well, as long as nothing breaks, anyway.  Audit the diskpool
volumes and you should be good to go.  If you're outside your reuse delay
period, tapes may have been overwritten.

I hope that helps.

Alex