It is not possible to change default Active Directory attributes using ActiveRoles. This is also not recommended by Microsoft.
You can, however create virtual attributes and have those displayed on the 'Other Properties' tab of user properties in the MMC or on the Web Interface.
For further information on creating virtual attributes and having them displayed on the 'Other Properties' tab of the user properties in the MMC please refer to KB 96578 at the link below:
For further information on customizing the Web Interface please refer to the 'ActiveRoles Web Admin Guide' documentation in the 'Customizing the Web Interface' section.