This option lists all the roles having the
edit_posts capability or, since version 3.2.3, the corresponding custom capability for a custom post type: selecting a checkbox enables the plugin for the corresponding role.
Users are allowed to copy the posts/pages of every other user: this means that password protected posts could be copied and accessed by other users, especially if the option
Author under Post/page elements to copy is disabled (so the current user will become the author of the copied post).
Roles enabled under this option have the
copy_posts capability. This doesn’t override other capabilities, so for example if a Contributor (which lacks the
publish_posts capability) copies an already published post (and the
Status option under Post/page elements to copy is enabled), the resulting post won’t have status
pending, accordingly to what happens when a Contributor wants to publish a post.