First of all, the new UI is horrible. It's clunky, difficult to use, has many bugs that don't allow people to scroll down the role menus for easy editing, convoluted and in same cases more laggy than the original UI.
The new UI is a fix for something that wasn't broken, it becomes gratuitious to make servers with large amount of roles and easily multiplies the time it requires to take. My suggestion is to either go back to the old UI, have an option in the server role menu to switch between the two, or create an entirely new one.
Furthermore, another suggestion that could work for easy role management would be [Role Categories], similar to server categories it would help sort large amounts of roles making the entire experience more streamline