Ansible role variables

I have Ansible 2.3.0.0 with this roles in playbook:

- { role: bwt-container, tags: ['bwt_en', 'bwt'], vars: { app_lang: "en" } }
- { role: bwt-container, tags: ['bwt_de', 'bwt'], vars: { app_lang: "de" } }
 

BWT application have various languages, which I would like define in vars. But when I run:

ansible-playbook -v site.yml --limit test-server --tags bwt_en 

So app_lang variable have “de” value…

Why??
I would like have 2 containers with various languages…
Do you anyone know how resolve it??