can var_prompt be included in a role?

I have written a simple play book master.yml,the main function is to lookup the roles and enter one as input for second playbook. But it doesn't prompt for the variables eventhough I used var_prompt role.

--- #master.yml

- name: show roles.
  hosts: nodes
  connection: ssh
  gather_facts: no
  tasks:
    - include: showroles.yml

- name: createdb and map roles.
  hosts: nodes
  connection: ssh
  gather_facts: no
  roles:
    - vars_prompt_role
  tasks:
    - include: createdb.yml

My directory structured as following:

/playbooks/createdbandmaprole/
[user@localhost createdbandmaprole]$ ls
createdb.yml  hosts  master.yml  roles  script.sql.j2  showroles.yml
[user@localhost createdbandmaprole]$cd roles
[user@localhost roles]$ ls
var_prompt_role
[user@localhost roles]$ cd var_prompt_role/
[user@localhost var_prompt_role]$ ls
defaults  handlers  library  main.yml  meta  tasks  vars
[user@localhost var_prompt_role]$ vim main.yml
vars_prompt:
 - name: "database"
   prompt: "enter the name of database"
   private: no
 - name: "role"
   prompt: "enter the name of role"
   private: no
 - name: "ad_group"
   prompt: "enter the AD_Group"
   private: no
[user@localhost createdbandmaprole]$ ansible-playbook master.yml -i hosts --check

but it doesn't prompt for vars