Barred Rock, and yes rooster if it is 12 weeks or younger.
Legs are yellow with some black wash. Marans have white-grey legs. French Marans have feathered legs...down leg and outside toe.
Another difference will be the barring. Barred Rock have a clear barring, almost like zebra stripes, and males are usually double barred so will have more stripes than females who will look darker...but often you can't see that difference until you have a male and female side by side....is it black on white or white on black.
Cuckoo is sloppier, almost a dappling look rather than crisp bars.