Not everyone in the ancient world ate chicken. While just about every ancient culture valued chickens for their eggs, by no means all were excited about their meat (the Japanese eschewed both and mostly kept chickens as exotic pets). The Romans are an excellent example. Avid egg eaters, they were extremely practical. They considered the eating of hens to be wasteful, an act only fussy, decadent pantywaists like, say, the Greeks would be capable of (here I should insert that there are notable parallels between the way the ancient Romans viewed the Greeks and the way some modern Americans view the French). The Roman author and naturalist Pliny the Elder wrote this about the inhabitants of the Greek island of Delos:
The people of Delos began to fatten hens, whence arose the revolting practice of devouring fat birds basted in their own gravy.
Sounds great to me, actually, but the Romans were not amused. In fact Roman society maintained a rigorous set of what were known as sumptuary laws to prevent exactly this sort of ridiculous extravagance. Sumptuary laws restricted excess in most of its forms: clothes, furniture, artworks, etc., and severe penalties were meted out for individuals found guilty of luxurious living.
But for every law there’s usually a loophole, and many Roman citizens and subjects went to great lengths to circumvent the sumptuary laws and get a literal taste of the good life. So where the law had plenty to say about hens, it said nothing about cocks. Which meant that as a Roman you were presumably free to fatten up a cock for the table by castrating it and allowing it to eat all it wanted. Such birds were known as capons and were frequently enjoyed boiled. Quite nice with caroenum!
Here I should add that while sumptuary laws were big in the early days of Rome, they became much less popular as the civilization peaked, grew decadent and declined. But the idea caught on in Europe where sumptuary laws were common all through the Middle Ages and beyond. Sumptuary laws existed in colonial America as well, but while Prohibition was denounced by then ex-president Taft as a modern example of a sumptuary law, none have existed here for well over 200 years. Which means we can roast a chicken any time we want without fear of retribution.