Ansible copy ssh key from one host to another

This does the trick for me, it collects the public ssh keys on the nodes and distributes it over all the nodes. This way they can communicate with each other.

- hosts: controllers
  gather_facts: false
  remote_user: root
  tasks:
    - name: fetch all public ssh keys
      shell: cat ~/.ssh/id_rsa.pub
      register: ssh_keys
      tags:
        - ssh

    - name: check keys
      debug: msg="{{ ssh_keys.stdout }}"
      tags:
        - ssh

    - name: deploy keys on all servers
      authorized_key: user=root key="{{ item[0] }}"
      delegate_to: "{{ item[1] }}"
      with_nested:
        - "{{ ssh_keys.stdout }}"
        - "{{groups['controllers']}}"
      tags:
        - ssh

Info: This is for the user root