I don't think that Rocco or Neri would have been smart enough to figure out that Roth was behind it. Tom MIGHT have been but why should he stick his neck out? His patron was gone and he wouldn't want to be seen as a threat by either of Michael's attack dogs. he certainly couldn't give them orders at this point.
I think Rocco and Neri would have blamed Pentangeli and threatened some sort of war. The Corleones tear themselves apart. Roth picks up the pieces in Nevada and overseas while the Rosatos get NY-if they're strong enough.
"When the snows fall and the white winds blow, the lone wolf dies but the pack survives."
Winter is Coming
Now this is the Law of the Jungle—as old and as true as the sky; And the wolf that shall keep it may prosper, but the wolf that shall break it must die.
As the creeper that girdles the tree-trunk, the Law runneth forward and back; For the strength of the Pack is the Wolf, and the strength of the Wolf is the Pack.
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