William,
It is considered best practice always to set the OSPF router-id manually, whether you happen to have a loopback or not. The reason for this is because there are certain OSPF functions that will break should the Router-ID ever change (an OSPF virtual link is a great example of this). If you rely on OSPF automatically choosing its Router-ID based on a loopback you have configured, this is no guarantee that the Router-ID wouldn’t change later (for example, you later needed another loopback for some other purpose, and this new loopback had a higher IP address than the first).
If you get into the habit of immediately setting the OSPF router-id as soon as you create the routing process, you will do yourself favors in the long run.