You're a beginer right? I don't mean to criticize you, everyone is a beginner at some point and is impossible to know everything from the start, even I was in your shoes ten years ago and you are doing right, is a good ideia to ask help when we don't know what to do, but there are some things that are making your battle difficult:
1º Is that you don't seem to have much experience with RPG games yet, for example, why putting rock smash and cut on Grovyle? This is the Job for the Hm especialist, you should separate the pokémons you will use to battle and the ones you will use for HM tasks, otherwise will be difficult to create a good setup of moves.
2º Is your personal skills, the basics, you have to use strategy and try to predict what he will do, you have to understand your enemy and his strategy and see how you can count against it, you have to plan against it
For example, you lost to him, but why did you lost to him? It can be alot of reasons, you have to idetify thoose reasons, to think about what would solve that matter, can even be more than one.
If you Believe is the move facade, like you stated, there are many options, among the easiests but also quick options include: Fast pokémon with strong fighting moves (not rock smash) can defeat him before he nail you, as long as your level is about the same as him os just a little under, second way of dealing against this move is using rock and steel type pokémons, especially if you have the move protect, aron is a pokémon that work preety well against him, using protect when he gonna use a move that is effective against aron, after it his slaking will be loafing around and his vigoroth doesn't have much to deal against aron. And about facade, it barely scrath iron who is rock/steel type. His vigoroth and one of his slaking doens't have much at all against a aron, you just have to pay attention against thoose two, only one of his slaking is a problem because it have focus punch, but even if you don't use protect to avoid the move he will use when he is not loafing around, in most cases you will still be able to hit him with any move and make him lost his focus so, even so is kinda easy, the slaking who have focus punch doesn't have nothing to put you to sleep, paralyze, lower your accuracy and etc. Only the other Slaking has yawn and his vigoroth have encore, but as long as you pay attention to thoose moves, is very easy.
But the easiest way (but not the quickest way) is just to use brute force, just grind your pokémon to at least five levels (or more, the number you need to surpass him) above his most powerfull pokémon and things will become automactly easy, you don't even have to worry much about moves or pokémons to use. After all, the point of thoose games is that you stop to grind once in a while, even if you don't like doing it, at least against the elite 4 and Champion is a place where gring is completely necessary, especialy on old games. (Not the case with the last ones who have the new reworked exp share/all)
If you don't like having many pokémons, in some cases is worthy at least catch and raise a pokémon that you don't want on your team but is effective against a situational fight, after he has done what he needs to do, you can just leave him on the BOX and not use him anymore.
His pokémons movesets can be seen here, so you can plan even better: https://bulbapedia.bulbagarden.net/wiki/Norman#Pok.C3.A9mon_Ruby_and_Sapphire
Hope I could help, I wish you success on your battle against him!