Hi, I would like to know if the starter needed for a single lamp ballast for a F4, F6, F8 lamp is the same or different for each of the following ballasts: 120V ( Robertson L48) , 240V ( Robertson L4835 ) , and 277V ( Robertson L6827 ).

Yes, as long as the lamp is a 4W, 6W, or 8W tube, an FS-5 or equivalent starter should work just fine at any of those supply voltages. I believe the important part is the lamp's voltage, not the main supply voltage, so there shouldn't be a difference.