Your role should look something like this:
- name: Node.js - Get script
  get_url:
    url: "http://deb.nodesource.com/setup_6.x"
    dest: "{{ var_node }}/nodejs.sh"
- name: Node.js - Set execution permission to script
  file:
    path: "{{ var_node }}/nodejs.sh"
    mode: "u+x"
- name: Node.js - Execute installation script
  shell: "{{ var_node }}/nodejs.sh"
- name: Node.js - Remove installation script
  file:
    path: "{{ var_node}}/nodejs.sh"
    state: absent
- name: Node.js - Install Node.js
  apt: name={{ item }} state=present update_cache=yes
  with_items:
    - build-essential
    - nodejs
- name: Node.js - Install bower and gulp globally
  npm: name={{ item }} state=present global=yes
  with_items:
    - bower
    - gulp