Mention new roles requirements.

readme.org

@@ -8,6 +8,9 @@
    - make sure you have the proper gpg key on your file system ( since we are using the "open the vault" method of protecting our passwords here)
    - Make sure you've got the posix ansible collection installed: ~ansible-galaxy collection install ansible.posix~
 
+** updating ansible roles
+TLDR: when updating the playbook and before running it, you'll need to run make roles to make ansible-galaxy download dependency roles (see the requirements.yml file) to the roles/galaxy directory. Without this, the playbook won't work.
+
 ** common scripts:
  ~ansible-playbook -i inventory/hosts matrix-docker-ansible-deploy/setup.yml --tags=setup-all,start~
    - this will upgrade your configured matrix things.