In the novel Lord of the Flies by William Golding, the author brings to a potentially cannibalistic conclusion the gradual decline and fall of the castaway boys from divine-looking choristers to near-cannibal savages. In fact, some critics may even say that this is doing a dis-service to cannibalistic tribes as the latter have never been taught any different and so can possibly be viewed as "innocent." These boys have been given the "best" in life in terms of education, affluent families and religious/moral guidance. Yet Roger and Jack in particular seem to fall fast into the abyss - in Roger's case this is all the more culpable because his actions are so often pre-meditated - as in the examples where he plans to harm Ralph and an "innocent" (Piggy) is killed in his stead. The sharpened stick at the end suggests gruesome ytibal consequences.
After first unleashing the boulder that kills Piggy in William Golding's Lord of the Flies, Roger has an even more gruesome end planned for Ralph. In the novel's final chapter, Roger is seen to have sharpened a stick at both ends, and he plans to use this on Ralph in much the same way as the fly-ridden pig's head has been treated: He plans to cut off Ralph's head and mount it on the stick. His ruthlessness surpasses even that of Jack, who would probably still be happy to continue hunting the wild pigs on the island.
Toward the end of the book, Roger tries to kill Ralph a number of times. In Chapter 11, Roger levers down the huge rock that was meant to kill Ralph. It kills Piggy instead.
In Chapter 12, Roger and others are hunting Ralph. They are going to try to hunt him down like a pig. Roger has sharpened a stick at both ends, we are told. The implication is that, after they kill Ralph, they are going to spit him on the stick and roast him like a pig.
So I imagine the answer that you are probably looking for is that Roger plans to kill Ralph and roast him.