The character has rarely appeared in American stories but appears regularly in Brazilian and European stories, and more often in Italian ones. His first appearance in an Italian story was Zio Paperone e il kiwi volante from 1963. Since then the Italian creators have further developed the character and have examined various layers of his relationship with Scrooge.
One of his main characteristics is his habit of eating his hat whenever he is defeated by Scrooge. In some stories, Rockerduck has eaten a whole truckload of hats because of his defeat.
Like his rival, he is a shrewd businessman and has managed to organize a worldwide financial empire that can easily rival those of Scrooge and Flintheart Glomgold. Unlike them, he is not a tightwad but rather a free-spending billionaire. Rockerduck has a taste for luxury, and likes to show off his wealth. Besides his secretary, advisor and right-hand man Lusky, he does not seem to have any close confidants.
Like Scrooge and Flintheart, Rockerduck is extremely competitive. He is rivaling them in the wealth department and has occasionally claimed the titles of "The Richest Duck in the World" and "The Second Richest Duck in the World". Since those titles belong to Scrooge and Flintheart respectively, it can be inferred that he owns the title of "The Third Richest Duck in the World", but this has not been explicitly stated in any major story. He is an influential member of the Billionaires' Club of Duckburg, of which Scrooge and Flintheart are also members. Only two stories feature him and Flintheart both, though: Zio Paperone e il bisbilione, and Zio Paperone e la disfida sulle punte.
Rockerduck also has a passion for collecting. Besides his valuable coins and stamp collection, he is also the owner of an extensive art collection, including artifacts created from antiquity through to the 20th century. Since Scrooge also has collections of the same theme and similar value, many of their confrontations center on them trying to obtain a new addition to their collections.
Many of the stories presenting him, especially during the 1970s and the 1980s, compare and contrast his and Scrooge's methods of organizing their business in order to gain profit. Some of those methods include researching new products for their industries, ways of refining and improving the existing ones, and the study of new producing methods. Also ways of improving their marketing techniques and public relations, in order to increase sales. Or even trying to improve the ratings of their TV stations and the sales of their newspapers, in order to have more clients paying for advertisements in them. Both he and Scrooge try to predict each other's moves in order to act accordingly. In his efforts, Rockerduck often resorts to industrial espionage or sabotage. Although less often, Scrooge occasionally uses the same methods. Sometimes Rockerduck's plans against Scrooge involve more severe actions like abduction, hijacking his planes or blackmailing him. On these occasions he usually lets his right-hand man Lusky do the dirty work, but he also hires the Beagle Boys to do his dirty work for him from time to time.
Oa more personal level, Scrooge and Rockerduck seem to bicker constantly, criticizing each other's ways of life and personal faults. However, even at times when Rockerduck has had Scrooge at his mercy, he has not attempted to kill his opponent. Although his confrontations with Scrooge have often found him defeated or even humiliated, he has commented on at least enjoying the challenge that Scrooge presents to him. At times the two find each other cooperating to achieve common goals. If they are worthy rivals to each other, they also seem to make effective partners — but only on a temporary basis. Some stories portray Rockerduck in a more positive light and portray him as friendly towards Scrooge's associates like Brigitta McBridge and Donald Duck, as he has nothing personal against them. When relaxed he can even be a pleasant companion for them or Scrooge. In all these traits, he differs from Flintheart Glomgold.
Barks never gave Rockerduck an origin. Don Rosa later provided him with one, in his series The Life and Times of Scrooge McDuck. According to Don Rosa, Rockerduck has several differences from both his fictional rival and his historical namesake. Rockefeller and Scrooge were born in poverty and worked to earn their fortunes. John D. Rockerduck was born c. 1878 (this is arguably in contrast to many stories where he seem to be at least 20 years younger than Scrooge) to Howard Rockerduck, an American millionaire who had earned his fortune in the California gold rush of 1849. While John's father was a shrewd businessman but a mild-mannered man, his mother was a rather snobbish woman who spoiled her son. Much to his father's disappointment, John learned at an early age to look down on everyone less affluent than his family as a "peasant". While his father tried to remind him that he was once poor too, John became as snobbish as his mother.
John's first meeting with Scrooge occurred in 1885, in Butte, Montana. At the time John was around 7 years old and Scrooge was 18 years old. Howard Rockerduck was heading to a meeting with Marcus Daly, an Irish businessman known as the "Copper King", to discuss his investments in "The Anaconda Copper Mining Company". Unsure of the way, Howard stopped to ask for directions. The person he asked was young Scrooge, at the time an unsuccessful copper prospector. Despite John's protestations, Howard started having a friendly discussion with the inexperienced prospector and ended up teaching Scrooge the secrets of the job, and helping him earn ten thousand dollars. While Scrooge had to leave for Scotland to attend to family business, John again protested against his father's relationship with the "filthy peasant". Howard, to whom Scrooge resembled his younger self, introduced his son to corporal punishment in an effort to teach him some manners. Judging from his later behavior, this did not work. John Rockerduck would later inherit his father's fortune and grow to become a rival of Scrooge. Over the years, he would grow his fortune, and eventually achieve the “Second Richest Duck in the World” title.
The story 'Il matrimonio di Zio Paperone', tells another tale about the origins of Rockerduck's wealth and his rivalry with Scrooge. The story is told by Scrooge's secretary, Ms. Quackfaster, to Scrooge's nephews Donald and Huey, Duey and Louie. Many years ago, when Rockerduck was a starting millionaire, he ran into Scrooge in the Millionaires Club. They started arguing and decided to settle their argument with a game of golf. If Rockerduck was to defeat Scrooge, he would win half of Scrooge's entire fortune. It looked like Scrooge was going to win. However, a bee stung him while golfing, so he missed the last hole, leading Rockerduck to win, which subsequently earned Rockerduck half of Scrooge's fortune.
Other stories have further traced the Rockerduck family history. Although some depict John as a distant cousin of Scrooge, through an unspecified genealogical connection, others have traced their rivalry to their ancestors. Arguably the most notable among the later stories is an eight-part saga named Storia e gloria della dinastia dei paperi. It depicts their family history, as a family feud that begun in Rome during the 1st century BC and continues to the 20th century.
John D. Rockerduck appears in the 2017 reboot series as one of the antagonists, voiced by John Hodgman. He made his first appearance as the main antagonist of The Outlaw Scrooge McDuck!. In the present, Rockerduck is revealed to be still alive and a member of F.O.W.L. He is frozen in ice and his enforcer Jeeves carrys him now.