I just found the following utility that could be used to remove roaming profiles that have not been used in more than X days:
https://helgeklein.com/free-tools/delprof2-user-profile-deletion-tool/
The only options I could find in GPO/Registry are delete profile immediately on log-off, or delete ALL profiles (including local) after X days of inactivity on machine reboot. Neither of these options are ideal for managing roaming profiles.