gistfile1.txt

# roles/test1/vars/main.yml
---
test_rolevars: TEST1_ROLEVARS

# roles/test1/tasks/main.yml
---
- debug: msg="testvar = {{ test_rolevars }}"

# roles/test2/vars/main.yml
---
test_rolevars: TEST2_ROLEVARS

# roles/test2/tasks/main.yml
---
- debug: msg="testvar = {{ test_rolevars }}"


$ ansible-playbook -i localhost, test.yml 

PLAY [Test role defaults] ***************************************************** 

GATHERING FACTS *************************************************************** 
ok: [localhost]

TASK: [debug msg="testvar = TEST1_ROLEVARS"] ********************************** 
ok: [localhost] => {"item": "", "msg": "testvar = TEST1_ROLEVARS"}

TASK: [debug msg="testvar = TEST2_ROLEVARS"] ********************************** 
ok: [localhost] => {"item": "", "msg": "testvar = TEST2_ROLEVARS"}

PLAY RECAP ******************************************************************** 
localhost                  : ok=3    changed=0    unreachable=0    failed=0   

# ./all.yml

---
- hosts: all
  roles:
   - role1
   - role2

# ./roles/role1/tasks/main.yml

---
- name: role1 step
  debug: msg="var={{ var }}"

# ./roles/role1/vars/main.yml

---
var: role1

# ./roles/role2/tasks/main.yml

---
- name: role2 step
  debug: msg="var={{ var }}"

# ./roles/role2/vars/main.yml

---
var: role2

# ./test
[all]
192.168.1.101


$ ansible-playbook -i test all.yml

PLAY [all] ********************************************************************

GATHERING FACTS ***************************************************************
ok: [192.168.1.101]

TASK: [role1 step] ************************************************************
ok: [192.168.1.101] => {"item": "", "msg": "var=role2"}

TASK: [role2 step] ************************************************************
ok: [192.168.1.101] => {"item": "", "msg": "var=role2"}

PLAY RECAP ********************************************************************
192.168.1.101              : ok=3    changed=0    unreachable=0    failed=0