This and other things indeed suggests Rocco was also in on it. I sill believe Michael sent Rocco to kill Roth as the ultimate revenge and for Rocco to show his loyalty and redeem himself.
There are several other threads on this very topic, but I'll quickly weigh in, anyway.
If Michael thought Rocco was guilty of that kind of treachery, he wouldn't need to send him on a "suicide" mission. He just would have killed him. Period. Neri would have been more than happy to oblige.
As far as "redeeming" himself? There's no redeeming yourself when you betray your Don. If Rocco was guilty (and I've never seen any direct eveidence that he was), he'd be dead. End of story.
