I don't think it was so much a matter of Rocco being 'expendable' as him being the best man to accomplish the job. Logic would dictate that had this been a less difficult and/or less important hit, it could've easily been handed down to reasonably experienced buttonman. However Rocco had to assure Michael that this would be done.
As for being 'expendable', ... this was the business they had chosen. Long term loyalty aside, you literally put your life on the line whenever you did a job for your Don.
Apple
Difficult task to shoot Roth? I don't see it. What was so hard about going up to a person in an airport in the 50's and shooting him? Actually I think it was quite stupid. Wasn't there a better way of whacking Roth and getting away with it. Was shooting him in the middle of a group of armed FBI men, the way to go?
