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 ("Uncle Scrooge and the flying kiwi") by Giampaolo Barosso and Giorgio Bordini, first published in March 1, 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 world-wide financial empire that can easily rival those of Scrooge and Flintheart Glomgold. Unlike them, he is not a tightwad but much more a liberal spender (but by no means a squanderer), he seems to maintain that "you have to spend money to make money", this trait makes his a natural antagonist to Scrooge, who is capable of going to absurd lengths to spare even trivial sums of money. Rockerduck has a taste for luxury, and likes to show off his wealth. Besides his secretary, advisor and right-hand man Lusky, he doesn't 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 three stories feature him and Flintheart both, though: 'Zio Paperone e il bisbilione' ('Uncle Scrooge earns a billion'), 'Zio Paperone e la disfida sulle punte' and Whatever Happened to Scrooge McDuck? (where Rockeruck and Glomgold both make a cameo in a future vision that shows both of them having been made bankrupt by Donald's Duck charity company).
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.
On a more personal level, Scrooge and Rockerduck seem to bicker constantly, criticizing each other's ways of life and personal faults. But 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 co-operating 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.
In many countries Rockerduck is almost as well known as Scrooge himself. In others, like the USA, he is relatively obscure and sometimes translators get him confused with Flintheart Glomgold, who is more widely known. That's odd, because the two characters look nothing alike. (Interestingly, in DuckTales, which Rockerduck never appeared in, Glomgold's revised character had borrowed some of Rockerduck's traits.) But he is certainly one of the most prominent characters appearing in Scrooge McDuck stories.
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 didn't work.) John Rockerduck would later inherit his father's fortune and grow to become a rival of Scrooge.
The appearance in The Life and Times of Scrooge McDuck was the only use of the character by Don Rosa.
The story 'Il matrimonio di Zio Paperone', created by Massimo DeVita (art) and Elisa Penna (story) 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 wasn't as rich as he's nowadays (he 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. He then won 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 ("History and glory of the Duck dynasty") by Guido Martina, Romano Scarpa, Giorgio Cavazzano and Giovan Battista Carpi, first published April 5-May 24, 1970. It depicts their family history, as a family feud that begun in Rome during the 1st century BC and continues to the 20th century.
In one story where Rockerduck was trying to ruin Scrooge's deal about cleaning the statue of Cornelius Coot, Lusky sheepishly tells him "You have no conscience, sir", to which Rockerduck replies "That's not true. I had a conscience a long time ago, but I'd rather not talk about that".
According to the story Whatever Happened to Scrooge McDuck?, Rockerduck (as well as Flintheart Glomgold) was made bankrupt by Donald Duck, after the latter had inherited Scrooge's fortune and turned it into a charity company. However, the end of the story reveals that it actually takes place in an alternate future, caused by Scrooge travelling 100 years into the future to retrieve his 1# dime.