Creating a database under a different owner

I'm trying to set up a role in Postgres which can a) Create a new Role b) Create a new Database c) Make that new Role the owner of the database d) Have no other rights (as far as is possible!)

I have tried this:

sc_1=# CREATE ROLE tenant_admin CREATEDB CREATEROLE;
CREATE ROLE
sc_1=# CREATE ROLE user1 IN ROLE tenant_admin LOGIN NOINHERIT ENCRYPTED PASSWORD 'xyz';
CREATE ROLE
sc_1=# 

Followed by (in another session)

tahaan@Komputer:~/projects/acme-project$ psql -U user1 -h localhost -d postgres
Password for user user1: 
psql (9.3.6)
SSL connection (cipher: DHE-RSA-AES256-SHA, bits: 256)
Type "help" for help.

postgres=> SET ROLE tenant_admin;
SET                                                                                                                     
postgres=> CREATE DATABASE "Tenant1" TEMPLATE "tenant_template";
CREATE DATABASE
postgres=> CREATE ROLE "owner1";
CREATE ROLE
postgres=> ALTER DATABASE "Tenant1" OWNER TO "owner1";
ERROR:  must be member of role "owner1"
postgres=> 

Background: The requirement is to have an automated function that can setup separate databases in a multi-tenant system. My hope is that this function can be performed by a role that does not have too much rights.