Rogue One: A Star Wars Story brought back several classic X-wing pilots for the film's final space battle, however, one of them, the most well-known one, was conspicuously missing. It turns out, that wasn't an oversight. Wedge Antilles is one of the few supporting characters to appear in all three of the original Star Wars trilogy. In fact, it was his appearance in Star Wars: A New Hope, which was the reason he couldn't appear in Rogue One. Because Wedge has clearly never seen the Death Star before, so he couldn't possibly have been involved in the battle around Scarif.
Rogue One: A Star Wars Story does a lot to try to evoke the fans connection to the original Star Wars. This is primarily done by bringing back classic characters like Grand Moff Tarkin via CGI. However, in the case of Star Wars' Red Squadron, the new movie was actually able to use existing footage that had been cut from the first Star Wars in order to bring the team back. However, Red Two, Wedge Antilles, was not there. As StarWarsNewsNet discovered, this wasn't simply an oversight. According to Pablo Hidalgo, A member of the Star Wars Story Group, he needed to be left out of the fight in order to avoid a continuity problem with the original film. When the Death Star attack squad first comes within sight of the Death Star in the original Star Wars, Wedge says, "look at the size of that thing." The only way that line works is if he's never seen the Death Star before, which means he wasn't part of the earlier battle.
However, that doesn't mean that Wedge doesn't appear in Rogue One. In actuality, Wedge is heard, but not seen. According to Skywalker Sound's Matthew Wood, actor David Ankrum voices Wedge on the radio at one point telling flight personnel to report and redirect to Scarif. This means Wedge was still on Yavin 4 during the battle. It's not explained why Wedge is still there. Perhaps Wedge doesn't actually join Red Squadron until they come back from Scarif a few men down. We know that Red Five dies during the battle, which is the position that Luke Skywalker ends up taking during the Death Star attack.
It shows that the folks creating Rogue One: A Star Wars Story were very aware that they were treading on dangerous ground when making the film. Dealing with material that immediately preceded the original trilogy was dangerous if they screwed anything up. The goal was to add depth to Star Wars, not to take away from it by creating continuity problems between the two movies. For the most part, the team succeeded.