Hello Hunk,
This could get complex, I think this would probably be best if left to the SMP user to define additional roles. If you look at the core SMP config file at - %programfiles%\Altiris\Notification Server\Config\CoreSecurity.config, you will see the core SMP roles are defined right at the top. So you could have something like this :
<security>
<roles>
<role guid="a unique guid" nameRef="your role name" descriptionRef="" />
</roles>
</security>
The tricky part comes in If you want to grant privileges and /or permissions to do various operations in the console using the new role, it is going to be more complex. You would want to do it in a way that does not overwrite the settings of existing privileges and /or permissions.