All in all, I think we can all agree this was the sloppiest scene in the whole film. So many plot holes (best term I can think of), draws so much confusion. According to the Godfather wiki, which I have learned to trust. Rocco was in the first drafts of III. Willy Cicci was also, but Joe Spinelli died young, before III. I've read he was replaced by Joey Zasa. I believe Rocco was written out in the final draft because as we all know, the films have always been about setting the mood, and putting you inside the minds of our primary characters. And in addition, In III there were so many new faces, probably no room to fit Rocco into the mix. It's sad though, he was always my favorite. I have an image of him right before he whacks Roth as one of my desktops.

It's almost painful to over analyze this scene. Personally, it's making me frustrated. I'm going to choose to remember it differently. Michael used Rocco or Neri to reach an associate with ties to Sicily, to hire a zip for the job. This seems to remedy the situation.

Here's my desktop:
I save this image because it's a high resolution pic of a pivotal Rocco scene, the actual still shot lasts for about 1/4 of a second.