A User Role is for using some pages, or some microflows, etc. except if you define an Administrator Role who has all the rights and accesses.
I don’t understand how a User Role could have several User Roles under.
If I translate well, you perhaps wants to create something like that:
Administrator
MasterRole1
ChildRole1
ChildRole2
ChildRole3
ChildRole4
ChildRole5
ChildRole6
MasterRole2
MasterRole3
MasterRole4
MasterRole5
MasterRole6
But each case will be different (otherwise why do you need to create a pattern like that?). Please, be more explicit.