He shows up in the Griffins' house after Peter Griffin had restored the original timeline in "Meet the Quagmires". Peter has altered the space-time continuium to have it that Roger now lives with the Griffins instead of the Smiths.
He makes a cameo in the Mos Eisley cantina scene in Blue Harvest.
Roger portrays Tiaan Jerjerrod in It's A Trap!.
Roger has a non-speaking cameo appearance in "Foreign Affairs".
The entire Smith family from American Dad appear as part of a cold-opening for "Bigfat", with the scenes that were originally intended for "April in Quahog". When the Griffins greet their new neighbors, the Smiths, who moved into Cleveland's old house, Peter sees Roger. Stan tries to keep Peter quiet but is forced to have to kill him as he starts to tell Quagmire about the alien. The entire opening turns out to be a dream by Hank Hill.
The DVD commentary for the American Dad! episode "Family Affair" revealed that the Griffins were to be one of Roger's adopted families with Roger having a close relationship to Meg.
Roger has a cameo in "The Simpsons Guy" appearing on Kang and Kodos' ship. He explains to the audience that they went to summer camp together.