What is the role of Rosencrantz and Guildenstern in the play?Why did Shakespeare place them in the play. Their effect on the themes, setting, plot, character development and relations, etc.
Critics have argued this question for years past, and most likely, will argue it for years to come. I have included an enotes link to an essay on this very subject, which you might want to read for further insight. Here is one possibility:
Shakespeare uses Hamlet the play and Hamlet the character to explore the theme of morality, action, and consequences. Hamlet struggles throughout the play to balance his morality with his desire to act in revenge of his father's death. He is unable to act, either against others or against himself, because he can not reconcile the two.
His foil, Fortinbras, is an impudent youth who acts without reflective thought. Though he seems to accomplish more than Hamlet, his actions seem without motive and the character himself seems immature and irresponsible.
Rosencrantz and Guildenstern act with motive, however their motive is out of blind faith. The respond to the commands of the King without concern to the propriety of the command. They actually ask for requests to be commands, implying that it is their duty to obey and they are therefore not responsible for their actions. Like Fortinbras, they are negative examples to the audience.
In addition, these characters provide opportunities to better develope the main characters. Through Claudius' and Hamlet's interactions with them, the audience learns more about the motives and personalities of both.