The beginning phrase of the soliloquy (“Now I am alone”) is rather interesting. It could truly be Shakespeare conveying to his (rather uneducated) audience that the character on the stage is actually, physically alone and no one will hear or see him or it could be something deeper - he is mentally alone, emotionally alone. He is alone because he, alone, heard the directions of the ghostly King Hamlet and he is alone because he can confide the directions of revenging the murder to anyone. His simple comment could, in four words, be the revealing moment of the bare essence of Hamlet’s character - he feels that no one understands him because of his situation and therefore he is alone.
The tone of the statement also seems to be sad and simple. It is a quick utterance of pure depression. However, the prince goes on to deliver an emotionally charged speech that is full of shouting and exclamations. This juxtaposition between the quick “Now I am alone” and the melancholy feel to the words and the powerfully exclaimed anger that follows shows how quick Hamlet can be to change mindsets and trains of thought.
Hamlet begins by calling himself a “rogue and peasant slave” because of his reaction to the player. Hamlet is appalled by how quickly the player could make himself into the character he was aiming to portray and how he could let that character envelop his entire being - becoming pale in the right moments, crying in the right moments - all for the mere purpose of art and entertainment. All for Hecuba! All for nothing!