The Grinch Doctor wrote:
Also, the added material that expands the story into two films are from The Return of the King appendices and covers what Gandalf was doing during his absences from The Hobbit narrative, i.e. investigating the Neucromancer at Dol Gundar (hence Galadriel's and Saruman's return and Radagast's appearance).
Though the attack on Dol Guldur is mentioned in the ROTK appendices' Tale of Years, pages 301-302 of The Silmarillion
go into a little more detail and explain the Radagast-Saruman connection: Saruman was actively searching for the Ring by this point and using a host of spies that included birds summoned by Radagast, who ( like the White Council ) did not yet know that Saruman had "fallen to the dark side" in Star Wars parlance. I expect to see this touched on in the films. Probably a Saruman-Radagast scene where Radagast looks troubled and turns away, and then we see Saruman looking evil.