I found an interesting site on symbols in heraldry, that says a cock (maybe any male bird, though, not necessarily a rooster?) is a sign of courage and perserverance.

[www.fleurdelis.com]

There is a rooster on the French angel coin that is also supposed to symbolize courage.

[www.amergold.com]

I found this site

[www.intermirifica.org]

on the history of Easter eggs among other things, but the eggs have their own symbolism, not related to chickens or roosters.