See if this changes anything.

roles/taskotron/resultsdb-backend/tasks/main.yml

@@ -7,11 +7,13 @@
 - name: ensure database is created
   delegate_to: "{{ resultsdb_db_host }}"
   sudo_user: postgres
+  sudo: true
   action: postgresql_db db={{ resultsdb_db_name }}
 
 - name: ensure resultsdb user has access to database
   delegate_to: "{{ resultsdb_db_host }}"
   sudo_user: postgres
+  sudo: true
   action: postgresql_user db={{ resultsdb_db_name }} user={{ resultsdb_db_user }} password={{ resultsdb_db_password }} role_attr_flags=NOSUPERUSER
 
 - name: generate resultsdb config