Sites like romhacking.net have continued to survive for years on end because they don't host the original binary images (ROMs in their case), which are of course copyrighted to their respective authors; thus, they are not allowed to be reproduced using unauthorised methods or redistributed via unauthorised channels. As far as I can tell, patch files, unless you're patching a 0KB dummy file with the entire content (which wouldn't be the case here - compare it to something like pushing changes to a repo on Git, where it compares the differences in the file and alters it accordingly), aren't illegal under any jurisdiction.
Reverse engineering also isn't illegal at all... however, using knowledge from leaked source code (or code that is under a non-disclosure agreement, such as from internal documents meant for company partners) alongside reverse-engineered code is also legally extremely questionable due to the dubious means of acquiring the code. This infamously was the subject of a lawsuit between Atari/TENGEN and Nintendo when the former cracked the 10NES chip using a combination of reverse engineering and documents that were only meant for developers/publishers: https://en.wikipedia.org/wiki/Atari_Games_Corp._v._Nintendo_of_America_Inc.#
Basically as long as the original binary isn't contained somewhere (an MD5+SHA1/2 hash and/or reasonable description such as a file version is perfectly acceptable), it should be fine from a legal point of view.
(For disclaimer purposes, I'm not a lawyer, so correct if necessary should someone be more qualified than me to talk about this topic.)