My brother has 6 laying hens. He has no roosters because they aren't necessary and don't lay eggs.
He feeds them food scrapes, mostly vegetative, which are donated by friends and family. I'm told that chickens readily consume anything except citrus. Crushed egg shells are good for chickens too but don't give them un-crushed shells or they will lean to consume their own eggs.
Supplementing table scrapes with a small amount of laying pellets seems to do the trick. They are allowed to browse around the year to eat bugs, weeds etc.