Castle Rock

1. In the beginning of the chapter Piggy tells Ralph to take the Conch to the Castle Rock.
2. Piggy is going to tell Jack that he needs the glasses for the signal fire.
3. When they approach Jack Ralph says they are going to appear civilized.
4. Roger challenged Ralph as they approached Castle Rock.
5. Jack has been hunting when the boys approach.
6. Ralph called Jack a thief which started their fight.
7. Samneric get tied up after the fight by Jack and his warriors.
8. When Piggy is pleading for decency Roger is on top of the cliff pushing the boulder.

Roger is responsible for Piggy's death. First of all, Roger is the one who let the boulder go. Not only that he made sure that Piggy was in the path of the boulder. The boulder was kept in control and Roger blatantly leaned on the boulder in order to push it over the cliff. I think he meant to kill Piggy, not just hurt him.