There are tons of Roblox exploits out there. While some are outdated and not working, let's explore how this works.
Exploits usually require regular updates. They either get patched intentionally, or the game developer introduces an update that changes the addresses inside the virtual memory. The way exploits usually work is with some sort of code injection. They inject a piece of code (some times a dll) inside a game that alters the behavior of the game. Because these dlls attach to a certain position and 'hook' functions, they do frequently need to be updated by the developers. The developer might attach to the function that checks the remaining ammo for example. By hooking this function and making it always return positive, might get the actual gamer unlimited ammo. Another example. The exploit developer might hook into the function that draws the walls in the game. By changing the opacity it is possible to remove the walls or make them see-through. A slightly more complex cheat might involve getting the position of each gamer on your screen and automatically aiming for it which is generally called an aimbot.
You have downloaded so many exploits and want to make your own thing. Unfortunately this is not an easy task. You need excellent skills in reverse engineering and spend countless hours digging through games to find how they work.
Once you know it, it might be an easy thing to do. But the path to achieving this might be bumpy. Knowing a lot about C++, operating systems and process manipulation is certainly desirable. The average person might need a few years just to learn the C++ programming language.
Just doing a small calculation and you might see that it requires a few thousand hours of learning and trial & error. Are you going to be the next scriptkid? Well there is enough incentive. The game exploit developers earn a decent amount of money to say the least. Whether it is a paid mod of game, or just a free version. The audience is massive.
What we usually see is that the free versions actually make more money. FileDM for example monetizes the free downloads. Eventually all the hard (developing & reverse engineering) work gets rewarded if you know what you're doing as a coder obviously. Taken into account the Youtube+Website Ads and on top of that the FileDM earnings, it is easy to say that some of these scriptkiddies outearn their parents. They bring joy and fun to so many gamers that are tired of the regular game, and want to explore some new fun stuff inside the games. On top of that there is this monetary reward which makes it all amazing for the select few that are actually able to do this. This is not to discourage anyone, but it will be a bumpy road to say the least. The skills earned to get good at this, might get you more in other things as well such as freelancing / paid programming jobs.