How to get all capabilities of an existing user role

I suggest not to mess with the existing roles and capabilities in its default, it might help you some trouble when you will have a bunch of custom roles and capabilities in the future.

To answer your question, I will have an example: I need new role/user group that has almost an Administrator but don’t have the the capability to edit plugins and the theme, to do that:

1. Let’s say you would like to copy the existing capabilities of Administrator, do it by:

   $admin_role_set = get_role( 'administrator' )->capabilities;
   

2. You can create a new user role by using add_role, see the handbook for more details. We can then use the list of capabilities that we have from #1 by using:

   $role="content_admin";
   $display_name="Content Admin";
   add_role( $role, $display_name, $admin_role_set );
   

3. By checking the Roles and Capabilities list from the handbook, we will be needing to remove edit_plugins & edit_themes capabilities, we can achieve that by using remove_cap():

   remove_cap( 'content_admin', 'edit_plugins' );
   remove_cap( 'content_admin', 'edit_themes' );