Need a user= here.

roles/clamav/tasks/main.yml

@@ -36,6 +36,7 @@
 - name: setup cron job for clam scan
   cron: >
     name="clamscan"
+    user=root
     minute="{{ clamscan_minute | default(35) }}"
     hour="{{ clamscan_hour | default(4) }}"
     day="{{ clamscan_day | default(*) }}"