Accessing inventory host variable in Ansible playbook

You are on the right track about hostvars.
This magic variable is used to access information about other hosts.

hostvars is a hash with inventory hostnames as keys.
To access fields of each host, use hostvars['test-1'], hostvars['test2-1'], etc.

ansible_ssh_host is deprecated in favor of ansible_host since 2.0.
So you should first remove "_ssh" from inventory hosts arguments (i.e. to become "ansible_user", "ansible_host", and "ansible_port"), then in your role call it with:

{{ hostvars['your_host_group'].ansible_host }}

[host_group]
host-1 ansible_ssh_host=192.168.0.21 node_name=foo
host-2 ansible_ssh_host=192.168.0.22 node_name=bar

[host_group:vars]
custom_var=asdasdasd

You can access host group vars using:

{{ hostvars['host_group'].custom_var }}

If you need a specific value from specific host, you can use:

{{ hostvars[groups['host_group'][0]].node_name }}