Let's have a vote.
Roger is the first person to suggest a vote for leader of the island in Chapter 1. This action indicates that Roger himself doesn’t wish to be in charge, but rather wants to be told who to follow, and how. This desire to follow a leader makes him the perfect lieutenant for Jack, and an apt torturer and terrorizer of other boys on the island.
I've been watching the sea. There hasn't been the trace of a ship. Perhaps we'll never be rescued.
In Chapter 2, Roger is among the first to suggest that life on the island might be a permanent situation for the boys. Since he does not believe they will be rescued, Roger quickly adapts to the power structures on the island and aligns himself with Jack. His priorities are not to the signal fire and Ralph’s attempted order, but to his own desires for violence and terrorizing the others.
You don't half look a mess.
Roger encourages the new barbaric look and atmosphere in Chapter 4 when Jack paints his face for the first time before a hunt. The face paint works throughout the novel to shield Jack and his hunters from their own individuality and humanity, giving way to mob mentality and group violence. By encouraging Jack, Roger demonstrates his blossoming desire to abandon civility for savagery.
We've got plenty of time!
In Chapter 6, when the boys set off to find and kill the beast, Roger insists on staying out late to continue hunting the beast. Roger has accepted that they aren’t getting off the island. They have all the time in the world, to him. His main goal is killing the beast and participating in the violence.
You couldn't stop me coming if I wanted.
Roger casually threatens Robert in Chapter 10, when he comes upon Robert keeping watch at Castle Rock. By this point, Roger has already been established as a sadistic and cruel boy. Robert explains the apparatus rigged to drop large boulders on enemies, which Roger finds exciting for its violence. This conversation foreshadows Roger’s barbaric murder of Piggy in chapter 11 when he drops the boulder on Piggy.