Rocco is a silverback gorilla who lives on Noah's Island. He has a rather pompous manner, often starting sentences with 'I'm Rocco and ...', to show that he is right. He was captured from Africa as an infant an lived alone in a zoo for twenty years, until his first mate Hettie arrived. Rocco was overjoyed when he first saw Hettie, but their relationship was short-lived: Hettie drowned in the shipwreck while she, Rocco and the other zoo animals were on their way to a new zoo.

When Rocco arrived on the floating Island, he was devastated by Hettie's death, but was able to revive Jasper, who had gone into shock following the shipwreck. When Noah saw Rocco's medical skills, which had been learned at the zoo by assisting the vet, he appointed him Chief Surgeon of the Island. Since then, Rocco performed several operations on other animals who were in need of help.

Rocco's best friend on the Island has always been Reg; when others criticise Reg's unorthodox behaviour, he usually responds, 'There's not a thing wrong with Reg.' He also has a close relationship with Woomera, although originally they did not usually get on well, calling each other 'blinkin' marsupial' and 'big ape'. In the episode 'Woomera Runs Away', he realised how much he loved the kangaroo and they started to become more friendly with one another. Much later, they even confessed to each other that they would instantly be mates if they were the same species.

Rocco never fully comes to terms with Hettie's death, but he eventually becomes the mate of Gertie, a female gorilla rescued from a crashed aeroplane by Noah and the Problem Walrus. Their relationship is occasionally unstable, especially while Gertie is pregnant, but they stay together nonetheless, and Gertie gives birth to their daughter at the end of the final episode, after they leave Diamantina. The baby gorilla is named Tina, after Diamantina, and Rocco vows that she will never see the inside of a cage.