In Rogue One, while on Jedha, our protagonists bump into characters that look very similar to Cornelius Evazan and Ponda Baba, the characters who bully Luke while in the Cantina on Tatooine. Is this a coincidence and a shout-out to the original trilogy, or are these mentioned to be the same characters in supplemental material?
Yes (but see below)
They're clearly intended to be the same characters, albeit traveling under their aliases of Roofoo (Cornelius Evazan) and Sawkee (Ponda Baba). They're positively identified in the Star Wars: Rogue One: The Ultimate Visual Guide as such.
That being said, these aliases were only confirmed in a Legends source (the old obsoleted Star Wars Databank article on Evazan) so it's theoretically possible, albeit vanishingly unlikely, that these are two entirely different characters who merely happen to look the same.
They certainly match the appearance of those two, as well as having their generally unpleasant attitude:
Jyn brushed against a passerby, then felt a jolt as someone shoved her to one side. Her hand went under her jacket, sought her truncheon, as her assailant snarled, “You better watch yourself!”
Spoiling for a fight. Her gaze caught the man’s face—a barely human mien distorted from burns or scarring—and moved to a second individual—Aqualish, all tusks and bulbous black eyes—behind him.
Rogue One: A Star Wars Story
That phrase about “watching yourself” is also very similar to the dialogue from A New Hope:
EVAZAN: You just watch yourself.
A New Hope
Curiously, the IMDB credits list a different actor (Michael Smiley) as having played Evazan. Either way, they agree that someone played Evazan in the film.
It generally seems to be a very intentional Easter Egg. We can’t be entirely sure, though, since Rogue One is not listed as one of their appearances in their Databank entries.