Creating a cron job with Ansible (ERROR! 'cron' is not a valid attribute for a Play)
crond.yml in your example is not a playbook. It is a tasks file (list of tasks), while playbook is a list of plays.

A play must have hosts directive at minimum. Please see http://docs.ansible.com/ansible/latest/playbooks_intro.html#hosts-and-users

This is a playbook:

- hosts: localhost
  tasks:
    - cron:
        user: "root"
        minute: "30"
        hour: "02"
        job: '/usr/bin/rsync -avhz -e "ssh" --rsync-path="sudo rsync" -H --delete --numeric-ids &lt;ipaddress&gt;:"/data/rsnapshot-backups/&lt;ipaddress&gt;" /data/rsnapshot-backup'
        state: present