Override parent web.config settings in the child web.config

I want to override the settings in the parent web.config in a child web.config in a sub-folder.
In my parent web.config the following section is defined.
<roleManager configSource="Configs\Generic\roles.config"/>
I do not want to apply the same configurations for a sub-folder. Precisely, I do not want any configuration for roleManager in my sub-folder.

What should I write in the web.config of the sub-folder so that I can avoid roleManager settings.