You can create another AdobeID using a different e-mail address and use as your second login.
One thing to notice, though, is that when using the AdobeHSAuthenticator there is no difference between a user with an AdobeID that is not the account/room owner and a named guest. Both will enter the meeting as guest and get promoted if you allow it.
If you want to experiment with different roles (because your application uses more than the standard roles provided by Cocomo) or you need to test with users with a "permanent" user ID you should look at external authentication, where you create your users and assign them the userID and role that you require.
The SDK comes with an example (sdk/examples/ExternalAuthentication) that may help you (look at the java or php code: they show a basic server-side application that generates the authentication tokens using the name and role that you set)
I had already implemented a login process similar to what you describe (and borrowed liberally from the sample code), but what I was more interested in was how I can create a second user account so that I can log in as a test account other than my developer account.
The easiest way is to create a quick login dialog which accepts username. From there take the output of that dialog and plug it into your AdobeHSAuthenticator. See the "LoginDialog" example in the SDK for more.
Once you get closer to something you want to deploy, you'll want to use external authentication to integrate with any existing login systems you might have. See chapter 6 of the Cocomo Developer Guide PDF for more details on your options there.