User and group should be created by the apt redis package.

playbooks/roles/redis/tasks/main.yml

@@ -29,12 +29,6 @@
   with_items: redis_debian_pkgs
   notify: reload redis
 
-- name: ensure the redis group exists
-  group: name={{ redis_group }} state=present
-
-- name: ensure the redis user exists
-  user: name={{ redis_user }} append=yes group={{ redis_group }}
-
 - name: update redis configuration
   template: >
     src=etc/redis/redis.conf.j2