Here's a simple diagram of how to set this up. You can do that at any point in your level system and multiple times even so enjoy!
It uses all the base commands found on the Setup page, you just have the added ability to set multiple reward roles for specific levels.
This may seem a bit complicated but once you go through it once, it's extremely easy and you'll love it. Take your time, if you have any issues, drop by the support server!
The examples above use role mentions for adding roles, this is not needed if you do not wish to use role mentions. Simply stating the rolename after the
>reward add command will work perfectly fine.