Wasn't that poem about Kun Peng? A giant fish in Chinese folk lore that transforms into a bird. Why did you translate this as Roc? Wrong mythology dude, those are from Arabic myths.
"In the northern darkness there is a fish and his name is K'un. The K'un is so huge I don't know how many thousand li he measures. He changes and becomes a bird whose name is P'eng. The back of the P'eng measures I don't know how many thousand li across and, when he rises up and flies off, his wings are like clouds all over the sky. When the sea begins to move, this bird sets off for the southern darkness, which is the Lake of Heaven."
^ taken from a better translation off of Wikipedia