Create a file called specs.empty in home/bob/ansible on the local machine as follows:
HOST=
MEMORY=
BIOS=
VDA_DISK_SIZE=
VDB_DISK_SIZE=
Create the playbook /home/bob/ansible/specs.yml which copies specs.empty to all remote nodes' path /root/specs.txt. Using the specs.yml playbook then edit specs.txt on the remote machines to reflect the appropriate ansible facts.

Create a file called requirements.yml in /home/sandy/ansible/roles a file called role.yml in /home/sandy/ansible/. The haproxy-role should be used on the proxy host. And when you curl http://node3.example.com it should display "Welcome to node4.example.com" and when you curl again "Welcome to node5.example.com" The php-role should be used on the prod host.