custom user role wordpress – grant guest access to edit.php without insert/update/delete

After you’ve created the new role, you need to add the capability to it using add_cap.
Check here for more info: https://codex.wordpress.org/Function_Reference/add_cap

I think that for your particular case, you could replicate an Author but then remove certain capabilities using remove_cap
https://codex.wordpress.org/Function_Reference/remove_cap