Maybe this makes the most sense.

playbooks/roles/common_vars/defaults/main.yml

@@ -161,3 +161,9 @@ common_close_all_caches: |
             cache = get_cache(cache_name)
             if hasattr(cache, 'close'):
                 cache.close()
+
+common_robot_rules: |
+  {% for item in NGINX_ROBOT_RULES %}
+  User-agent: {{ item.agent }}
+  Disallow: {{ item.disallow }}
+    {% endfor %}