This may not be news for some of you, but for someone like me who hasn’t bothered to pay attention to the new EU, this did at least clarify some of the possibilities as to what rank/position Mendelsohns character might hae in RO;
http://www.starwarsnewsnet.com/2016/04/speculation-ben-mendelsohns-character-in-rogueone.html
Also, some rumors as to who might be playing Vader;