While the time frame of the movie would certainly allow for a Darth Vader appearance, some sources are reporting that Vader is not the role Wilding will be playing in the film.
Of course, this leads one to wonder if that means that Darth Vader will be making an appearance in the movie.
Since the Untitled Han Solo movie is currently filming, something that we know is happening considering everything that’s been going on with that movie behind the scenes, it would seem that Spencer Wilding has a role in that movie.
Since we never actually see the actor’s face in Rogue One that certainly opens up the possibility that he could be playing someone or something else; there’s no reason he can’t and it’s likely easier for Lucasfilm to call on somebody the company has worked with before then to bring in somebody new.