How to create custom role information instead of using built-in role database,

Hello Guys,
Usually in sub-folder we will limit the access right to some roles and this feature requires pre-defined database schema. 
However, if i still want to use this role feature of asp.net, but I do not like the pre-define database schema, I want to extract role information from my own database table and bind it to the role.
How can I do that?
Thanks. 
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