What Sex are my Cornish Roasters?

[FayoumisFreak]

Look for birds that have more red and more comb/wattle development than the rest. Most of those will be your cockerels. In your 2nd photo, of the two birds together at the top, the bottom one appears to be a cockerel. However, it is difficult to tell at this age.

 

[Xlcandylx]

Correct me if I'm wrong but I know bright red combs would be the first sign of boy. Plus once they become more feathered you can tell back the way there feathers come in around the neck and back. Like most rooster there feathers around the neck and back come out thin and to a point. Females will come out like a leaf covering there body.