We know that Rogue One: A Star Wars Story went through some significant reshoots after the end of principal photography. Now, the editors who put the final film together have opened up about exactly what got added to make the movie what we saw in theaters. It sounds like Rogue One was a very different film. While third act reshoots were significant, there were also additions made to the beginning of the film that had to be dealt with throughout the entire story.
They gave you the film that you see today. I think they were incredibly helpful. The story was reconceptualised to some degree, there were scenes that were added at the beginning and fleshed out. We wanted to make more of the other characters, like Cassian's character [Cassian Andor, the Rebel spy played by Diego Luna], and Bodhi's character [Bodhi Rook, the defected Imperial pilot played by Riz Ahmed]. The scene with Cassian's introduction with the spy, Bodhi traipsing through Jedha on his way to see Saw, these are things that were added. Also Jyn [Jyn Erso, the reluctant leader of the film, played by Felicity Jones], how we set her up and her escape from the transporter, that was all done to set up the story better. Of course, things like that have a ripple effect all through the movie so there was a lot of work to do, and as Colin said, there were three of us, we rolled up our sleeves and we got to work and made the movie you see.
We'd heard that a lot of the reshoots in Rogue One: A Star Wars Story were done to change the end of the movie. John Gilroy, one of three editors of Rogue One, confirms that this is true, but he also tells Yahoo Movies UK that they made changes to the beginning as well. It appears that our first exposure to several of the films' characters wasn't originally designed to happen as it did. We seemingly wouldn't have met Cassian Andor until Jyn met him at the rebel base. This means we wouldn't have known what sort of man he was until much later in the film. The intro scene with the spy gives us a much clearer view of the lengths he's willing to go. We apparently also would not have seen how the Rebels get their hands on Jyn. It seems the movie would have opened on the rebel base without much prolog.
Of course, While much of the reshoots created new material, we have to assume that they also replaced old material as well. There were a lot of scenes that we saw in trailers that never made it into the finished movie. If the reshoots were responsible for making the movie that we got, one becomes curious what sort of movie we would have received had the reshoots never happened.