Once the grades are finalized by an instructor there is some flag or button which indicates that the grades of this course has been finalized by an instructor. Like in PeopleSoft Campus Solution, initially the status of grade roster is "Not Reviewed" once the instructor has finalized the grade they clicks on "Update" button, then the status of grade roster has been changed from "Not Reviewed" to "Approved". So, admin can easily fetch a report who has not finalized their grades.

Thanks