Rebels characters (General Syndulla, Chopper) and ship (the Ghost) were in Rogue One if you are going to be a movie stickler.
A large amount of content was added from Rebels and it will continue to be a source of canon content. Filoni has also had his third animated series green-lit by Disney, so he will continue to be a source of canon content for the Star Wars universe. People who keep turning a side glance at Rebels or The Clone Wars need to get over it, as it is canon material and you are about to get more of the same. It aint EU.