Hi @patfm,
Using Canvas Data the the pseudonym_dim.sis_user_id will identify users who were created with an SIS_ID. Manually created users could have an SIS_ID if they were added via the UI, but this will depend on your process.
You could JOIN (user_dim and pseudonym_dim) your enrollment_dim for TA's and look for those without an SIS_ID.
Another option would be to use Account Reports
*.instructure.com/accounts/self/settings#tab-reports
The Provisioning Report particularly can be useful here, as you can get the users and role, and remove all users that aren't currently found in your SIS, or delete that role for all users where user_id (user sis_id) is null.