For operators who are not rostered on that day, you can tick a setting to hide their column, which means that only rostered on operator columns will display in Appointments.
To only show rostered on operators, go to Settings then into Appointment & Roster Settings. Tick Only Show Rostered On Operators, and Save.
Note: If you haven't already done so, also tick Automatically Roster Operators Off, so that means that all you need to do now is use your Roster to roster operators ON, and all time outside of their Rostered On hours will be shaded as Rostered Off.
Go ahead and use your Roster to roster your staff on. All those who are not rostered on will now have their columns hidden on those days that they're not in.
Only the operators who are Rostered On are displayed in Appointments.