What does Roger believe about the beast in Lord of the Flies?

Roger is referred to as the "dark boy." He is a natural sadist who becomes the "official" torturer and executioner of Jack's tribe of savages later on in the novel. Throughout the novel, Roger does not openly voice his opinion concerning the beast and fails to enter the group's conversation about the existence of a beast in chapter 5. However, the perspective of the group changes after Samneric swear that they encountered the beast on the top of the mountain. Interestingly, Roger volunteers to join Jack and Ralph in their search for the beast as they travel toward the top of the mountain in chapter 7. At the top of the mountain, Ralph sits beside Roger. Golding writes, 

Roger, uncommunicative by nature, said nothing. He offered no opinion on the beast nor told Ralph why he had chosen to come on this mad expedition. He simply sat and rocked the trunk gently (Golding, 94).

Golding reveals that Roger shares no opinion on the beast, and his reasoning for joining the expedition is unknown. However, one can assume that Roger has a keen sense of Jack's malevolent personality and simply follows his lead, knowing that Jack will eventually ask him to hurt someone. For the remainder of the story, Roger continues to follow Jack's lead and offers no further opinion concerning the existence or nature of the beast.