Glenn Danzig & Roy Orbison

Where did you hear that? Roy died in 1988 so it's possible but this might be a little far fetched. There is no mention of Roy in any of Danzig's albums up through Blackacidevil. You would think he would be credited for any additional songwriting. I doubt Roy would have helped when Glenn was in the Misfits or Samhain since Glenn was much younger and I would assume not well known enough to team up with Roy. These are my theories and I could be wrong but you never know...
 
They did work together. They did not do a duet, but Glenn wrote a song for Roy called Life Fades Away. It was Roy's last recorded song. You'll find it on the soundtrack for Less Than Zero. Glenn does a song on there called You And Me. Both songs are really good. Slayer also does a good cover of Inna Godda Da Vida on the soundtrack.