Do you need a roster for hens to lay eggs?

No,they lay eggs by them selfs but if you want CHICKS you need a roster to mate with thus they have chicks not eggs the normal ones.
No, a hen will lay eggs regardless of there being a rooster so long as she is kept comfortable and happy with a safe quiet place to lay her eggs. A rooster is needed if you want to breed more chickens since he will fertilize the eggs.