Ansible- Define variables based on conditions with if elif else

I have multiple roles as follows : haproxy, java, nginx, tomcat

├── ansible-test-host.yml
├── hapoxy
├── java
├── myplaybook.yml
├── nginx
└── tomcat

Base playbook is : myplaybook.yml and looks like below:

---
- hosts: test-local
  connection: local
  vars:
    java_version: "1.8.0"

  roles:
    - java

So my requirement is depending upon the roles specified java/tomcat/nginx etc I have a template file to populate. Say my logic is to do as follows:

if 
    role == java then in  template.j2  I have to set `JAVA_TOOL_OPTIONS= -Xmx10g -Xms5g` 
elif 
    role == tomcat then in  template.j2  I have to set `JAVA_OPTS= -Xmx10g -Xms5g` 
else    
    NOTHING 
endif

I have other underlying scenarios to sort but if I get the base of it rest I can do.

What I have tried in java role main.yml is here

---
# tasks file for java
- name: output the 'ansible_' magic variables
  debug:
    msg: [
      "ansible_role_names = {{ ansible_role_names | default({}) }}",
      "ansible_dependent_role_names =  {{ ansible_dependent_role_names }}",
      "ansible_play_role_names = {{ ansible_play_role_names | default([]) | join(',') }}"
    ]

- name: set facts
  set_fact:
     DEFAULT_VAR: >
                {% if "{{ ansible_play_role_names | default([]) | join(',') }}" == "java" %}
                JAVA_TOOL_OPTIONS
                {% elif "{{ ansible_play_role_names | default([]) | join(',') }}" == 'tomcat' %}
                CATALINA_OPTS
                {% else %}
                NOTHING
                {% endif %}

- name: output my custom var- try1
  debug:
    msg: >
        {% if "{{ ansible_play_role_names | default([]) | join(',') }}" == "java" %}
        JAVA_TOOL_OPTIONS
        {% else %}
        NOTHING
        {% endif %}


- name: output my custom var - echo 
  debug:
    msg: "{{ DEFAULT_VAR }}"

My output is as

TASK [java : output the 'ansible_' magic variables] ****************************************************
ok: [127.0.0.1] => {
    "msg": [
        "ansible_role_names = ['java']",
        "ansible_dependent_role_names =  []",
        "ansible_play_role_names = java"
    ]
}

TASK [java : set facts] ********************************************************************************
ok: [127.0.0.1]

TASK [java : output my custom var- try1] ***************************************************************
ok: [127.0.0.1] => {
    "msg": " NOTHING \n"
}

TASK [java : output my custom var - echo] **************************************************************
ok: [127.0.0.1] => {
    "msg": " NOTHING \n"
}

PLAY RECAP *********************************************************************************************
127.0.0.1                  : ok=5    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0   

Please help with pointers to achieve this.