Correct me if I am mistaken but I believe what you are looking for is the work that your resources are assigned to do during a given time frame, whether they entered the time in timesheets or not (i.e. Unsubmitted, Submitted or Approved)... Before there are any timesheets, there are NO timesheets, so you cannot report on this.
What you can report on is the Work allocated to Resources. You can look at their Resource Load and even create reports on their Load (allocated work). This will give you a sense of how much work they have been given, versus how much time they have submitted on those tasks.
Note that there are a number of out of the box reports that will show you informatioin by Task, Resource or Project as well as Resource Load information that may help you. Also, you can send Time tracking updates to resources (Timesheet Reminders) to remind your users to fill out their timesheets for their tasks. This is a setting in System Settings --> Time Tracking.