Roger was a chef on board the Albatross.
He tried to prevent the poisoning of the ship's crew, but got knocked out. Homer is convinced that Roger was really the murderer and so he tries to kill him by knocking him off the boat. Homer and Marge later find the Albatross and find out that Roger was telling the truth. Roger gets back on board and, to cover up the attempted murder, Homer kills him with a harpoon gun and gets away with it.