There are SueprMarioBros. edits where they only distribute the patching file and the patcher program... just not the original ROM itself. They leave that for you to find somewhere...
If it were to avoid a patent infringement then it could still be considered contributory infringement - ie you [knowingly] provided the necessary parts, methods, information that enables someone else to perform the infringement.
That's not going to be the case here as the code is too old to be patent encumbered.
Things are certainly moving towards there being a wide definition of contributory copyright infringement, eg cases against torrent file sites that don't store copyright works. It would be pretty asinine and regressive to punish someone for publishing instruction on a copyright work could be modified, IMO, but the law isn't known for always making sense.
There are SueprMarioBros. edits where they only distribute the patching file and the patcher program... just not the original ROM itself. They leave that for you to find somewhere...