Rosencrantz and Guildenstern are characters in the notorious play Hamlet. They are two confused men, who cannot differ there identities. In Shakespeare's play, they have minor parts, but in Tom Stoppard's play, they are the main protagonists.
The whole play runs congruent to Hamlet, some scenes' are taken directly from Hamlet, and the rest is almost like a behind the scene's look at Rosencrantz and Guildenstern. It shows these two men doing what the play Hamlet doesn't let you see. The two make witty remarks, and lead next to worthless lives, there fate is known, and their ignorance succeeds them to be perfect bait for Hamlet's plan to escape death in England.
Rosencrantz and Guildenstern have an important purpose in Hamlet. They may just be minor characters, but they are Hamlet's friends. King Claudius orders them to spy' on Hamlet and find the reasoning for his madness. And after Hamlet stabs Polonius, King Claudius orders for Rosencrantz and Guildenstern to escort Hamlet to England, where he will get his head cut off.
They spend the boat-ride to England discussing death. When they accidentally open the letter to the King of England (ordering Hamlets death) and read what Hamlets faith is, they don't know how to react. Rosencrantz and Guildenstern decide to just let it happen, for that must be Hamlet's faith. However, when they were asleep, Hamlet switches the letter to say that Rosencrantz and Guildenstern are to be-headed. In England Rosencrantz and Guildenstern react to the change very outgoing, by thinking that death is nothing to fear, that it's fate.