playbook: Add Router Advertisement role for gnet-re6stnet playbook

playbook/gnet-re6stnet.yml

@@ -23,5 +23,12 @@ Your token
       private: no 
       default: "notoken"
 
+    - name: "enable_router_advertisement"
+      prompt: "Enable Router Advertisement"
+      private: no
+      default: 'no'
+
   roles:
     - re6stnet
+    - role: routeadv
+      when: enable_router_advertisement == 'yes'