Rockerduck is mainly used in italian stories as Scrooges arch-rival instead of Flintheart Glomgold.
John D. Rockerduck is one of the main rivals of Scrooge McDuck. He is a wealthy businessman and has often made claims to the titles of "Richest Duck in the World" and "Second Richest Duck in the World", titles belonging respectively to Scrooge and Flintheart Glomgold - presumably he's just the Third Richest Duck in the World.
He debuted in the story "Boat Buster" (December, 1961) by Carl Barks. The story involved a motorboat race where Scrooge and John compete. Their motivation was to establish their own fuel as the best in the market. Barks never reused him. However the story "Zio Paperone e il kiwi volante" ("Uncle Scrooge and the flying kiwi" March, 1963) by the Baroso brothers established him as a major character in Italian-produced stories.
Rockerduck runs a world-wide financial empire out of Duckburg. Unlike McDuck and Glomgold, Rockerduck enjoys the luxuries made available to him through his immense wealth. He also does not hesitate to spend more money for various business projects than his tightfisted rivals would. This often includes better salaries and benefits for his employees. Stories featuring him and Scrooge often compare and contrast their management styles and their reactions to spending and investing. His downfall is that more often than not his projects and products involve better style but equal or lesser quality to those of Scrooge. On the other hand he can be quite ruthless and masters a network of industrial spies and saboteurs. Like Scrooge, John is a skilled manipulator and their schemes and counter-schemes tend to employ many pawns and greatly affect the lives of fellow Duckburg residents.
McDuck and Rockerduck tend to get on each other's nerves and their personal arguments tend to be reduced to exchanges of insults and memorable fist fights. This has not stopped them from forming alliances to pursue common goals, in business or other fields. While Rockerduck is often depicted as a snob, various stories have featured him in a somewhat better light. He can be quite friendly or charming when he seeks an alliance with someone or simply seeks some relaxation with a random companion. He has often managed to recruit various allies and enemies of Scrooge in alliances or working relationships. Rockerduck himself has only one loyal confidant, Lusky. The latter serves as his secretary, advisor, chief spy and right-hand-man.
In his early appearances, Rockerduck vowed to eat his hat if he failed to prevail in a confrontation, and over the years this trait has become something of a running gag. More and more stories depict Rockerduck literally eating loads of hats whenever he suffers defeat or even merely feels second-best.
Rockerduck is depicted as a coddled brat, whom his father Howard Rockerduck feels should be horsewhipped (and, it is presumed, is).
Rockerduck is a member of the Sinister Seven, in the guise of Rolla Dollar. Why he has joined this gang of ne'erdowells is as yet unknown.