Gareth Edwards and his creative team discovered some old film canisters while rummaging around the Lucasfilm warehouses. When he asked what they were, an employee said they were old Star Wars: Épisode IV - Un nouvel espoir (1977) footage. The discovery led to the inclusion of unused Episode IV material featuring Red Leader and Gold Leader in this movie.
Alan Tudyk, who plays K-2SO, improvised both the slap across Cassian Andor's face on Jedha and the line, "And there's a fresh one if you mouth off again." This improvisation made Diego Luna break character as Cassian and crack a smile that can be seen in the final film.
R2-D2 and C-3PO have a brief cameo, making Anthony Daniels the only actor to appear in every movie. (He appears as another character in Solo: A Star Wars Story (2018)).
Anthony Daniels was jokingly disgruntled that Alan Tudyk was allowed to play K-2SO in the relative comfort of a motion-capture suit, whereas Daniels had to endure years of discomfort and injuries in the C-3PO costume. Daniels laughingly cursed at Tudyk after Rogue One's premiere. Tudyk later said that a "Fuck you" from Daniels was one of the highest compliments he had ever received.
The studio had only two choices to play Chirrut: Donnie Yen and Jet Li. Yen was approached first because of his salary of $4 million against Li's $10 million. To gauge his interest and as secondary plan, director Gareth Edwards also offered him the other role of Baze. Yen expressed interest in playing Chirrut but was hesitant in accepting it, because it required him to be away in London for five months. However, it was his young son's love of the Star Wars films and comics that wore down his reluctance, and it was his idea to make his character blind.
Warwick Davis: The Star Wars veteran actor plays Weeteef Cyu-Bee, one of Saw Gerrera's militia members.
Rian Johnson: Star Wars : Épisode VIII - Les Derniers Jedi (2017) writer/director plays an imperial trooper controlling the Death Star's superlaser.