The artbook says, 'Its head detail resembled that of a frilled lizard', which can be clearly seen in the screenshots. Its wings seem thin and leathery, like that of a bat. Its neck is very long, because 'I actually wanted to do a long-necked bird-type'.
Roc was fought in a desert-like landscape, instead of a lake as with Avion. According to the artbook, 'Roc. You'd shoot it down with the bow.', meaning that the bow and arrow were vital to defeating this colossus, similiar to Phalanx. Because Agro can be seen in several screenshots, it is likely that she was necessary for defeating Roc by chasing it, again similiar to the battle with Phalanx.
- The Shadow of the Colossus trailer from March the 5th shows a short clip of the battle with Roc, in which Wander is seen riding Agro while the colossus attacks from above. The full trailer can be downloaded here (played at 1:55).