Actor Jimmy Smits had already confirmed back in August that he would have some role in Rogue One during an interview on The Talk after sharp eyed fans called out that they spotted him in a released sizzle reel.
When asked about it, his response was a coy smile and said, "can you say 'Cameo'? Can you say 'small part'?" You can see the relevant portion at round the 0:25 mark in the video below.
Today, equally sharp eyed @IndianaJedi spotted a photo of Smits in the latest edition of Us Weekly. Along with a small quote from Smits to the Weekly:
[Bail Organa's garb] isn't as stately as in the other episodes. He isn't as high up in the political food chain.