Simon is a type of Christ-like figure. He represents goodness:
Among all the boys, it is Simon whose behavior is perhaps the most exemplary during the first part of the story.
Simon picks fruit for the littluns who are too small to reach it. He meditates on things to help all the boys. He learns that the beast is a only parachutist. With that new knowledge, he can hardly wait to share his good news. He comes rushing out of the forest only to meet his sacrificial death. He is killed most barbarically. His death can be compared to the Crucifixion scene of Christ. The boys kill him with their bare hands and teeth. His death reawakens Ralph's sense that civilized order is a necessity in order for them to survive.
Roger represents evil. He is demonic. He treats everyone with hostility. He cruelly probes the sow's rectum with his spear and twists with all his weight until the sow screams in agony. Roger is merciless:
They corner the wounded pig, and when she falls they are on her. Roger is particularly cruel, driving in his spear slowly by leaning his weight upon it until the sow screams in agony.
Likewise, Roger kills Piggy with no remorse. Also, he is preparing to kill Ralph:
He prepares a stick, with points sharpened at each end, on which to mount Ralph’s head.
Roger is definitely savage in his ways. If Simon represents a Christ-like figure, Roger represents the anti-Christ or Satan. Truly Simon and Roger are extremely opposite one another in actions. Simon represents goodness in Roger's evil world.