You don’t have to have a pass at all for roughing to be called. It should have been off-setting penalties, at least.
By rule there must be a legal forward pass to have roughing the passer. The foul is called roughing the passer not the quarterback. There are special protections for a player who throws a legal forward pass. The foul for landing with full weight on the passer is one such special privilege of the passer. As a legal forward pass was not thrown, by rule there can be no roughing. Unnecessary roughness is a universal foul that cannot be negated by another illegal action. However unnecessary roughness is not called with the full weight landing as it is legal against all other players
Thus, by rule, this play cannot lead to any fouls with a call of roughing the laser due to the fact that an illegal pass was thrown. You are incorrect in your interpretation of the rule.