Its an interesting theory, but I don't think it is the case. Rocco lost out on a power struggle with Neri, and I think he went on the suicide mission to kill Roth to show his loyalty and nothing more.

"Io sono stanco, sono imbigliato, and I wan't everyone here to know, there ain't gonna be no trouble from me..Don Corleone..Cicc' a port!"

"I stood in the courtroom like a fool."

"I am Constanza: Lord of the idiots."