I checked the usually reliable centralized collection of mass knowledge known as Wikipedia. Sure enough, what was written there was in line with my colleague's comments: "The rasagolla was invented in the state of Orissa, where it has been a traditional sweet dish for centuries. The recipe for making rasagollas eventually spread from Orissa to neighbouring West Bengal. This was during the Bengal renaissance when Brahmin cooks from Orissa, especially from Puri, were routinely employed in richer Bengali households. They were famed for their culinary skills and commonly referred to as Ude Thakurs (Oriya brahmin-cooks). As a result, many Oriya delicacies got incorporated into the Bengali kitchen".
It goes on to explain that a man named Nobin Chandra Das of Bagbazar, Kolkata "modified the original recipe to extend the shelf life of the highly perishable sweet" and made it more marketable to the masses. Looking for further verification on the origins of the sweet, I checked Yahoo! Answers and the results were the same:
"By the time the recipe reached Nobin Das (which was either in 1868 or a few years earlier through another confectioner, Haradhan Moira), it was already a traditional item in Orissa - standard fare in the cities of Bhubaneswar and Cuttack, and of course in Puri."
Jayanta Mishra mentioned that "One can easily see how the popular misconception that Rasagulla originated in Bengal arose. It gained nationwide popularity only via Kolkata, with its better marketing infrastructure. Besides, one must not forget that when Rasagulla became popular, the state of Orissa was itself a part of the province of Bengal under the British". The only related article of interest yielded by Google Scholar was on the prevalence of coronary heart disease in Kolkata due to the eating habits and sedentary lifestyle of its inhabitants. For true lovers of the sweet delight, it does not matter who invented the rosogolla but that someone did.