$ cat defaults/main.yml
authorized_keys: /etc/ssh/authorized_keys
users:
  - name: root
    pass: passwordhash
    ugid: 0
    pubkeys:
      - key1
      - key2
  - name: user1
    ugid: 1000
    pubkeys:
      - key1
      - key2

-----
$ cat tasks/main.yml
---
- name: group | {{ item.name }}
  group: >
    name={{ item.name }}
    gid={{ item.ugid }}
    state=present
  with_items: users

- name: user | {{ item.name }}
  user: >
    name={{ item.name }}
    uid={{ item.ugid }}
    group={{ item.name }}
    password={{ item.pass | default('!!') }}
    comment={{ item.name }}
    shell={{ item.shell | default('/bin/bash') }}
    state=present
  with_items: users

- name: file | {{ authorized_keys }}
  file: >
    path={{ authorized_keys }}
    state=directory
    mode=0755

- name: template | {{ item.name }}
  template: >
    src=authorized_keys.j2
    dest={{ authorized_keys }}/{{ item.name }}
    owner=root
    group=root
    mode=0644
  with_items: users

-----
$ cat templates/authorized_keys.j2
{% for user in item.pubkeys %}
environment="GECOS={{ user }}" {{ lookup('file', user + '.pub') }}
{% endfor %}