Rosencratz tells Hamlet that he is as well as "the indifferent children of the Earth," powerless in the face of the will of the gods. Does he really have any options in compliance with Claudius' and Gertrude's demands?
I think I might have misread your question, Jamie. Are you asking if Hamlet has options, etc., or if Rosencrantz does? Because the line is said by Rosencrantz about himself and Guildenstern, aren't we really asking if Rosencrantz feels like he has any choices?
My Bevington textbook says that "indifferent" means "ordinary, at neither extreme of fortune or misfortune." So it seems like Rosencrantz is saying they're stuck in the middle - They have no fortune yet because their lives hinge on what they accomplish for the king and queen, but neither do they have misfortune because if they do what they've been "asked" (coerced) to do, then all will be well for them in the future.
Remember, too, that Rosencrantz was the one who makes the reference to Claudius and Gertrude putting their "dread pleasures more into command than to entreaty." It would thus make sense that he would be the one to say that they're stuck, with no choice in the matter but to obey the "dread pleasures" of the king and queen.
I think there is also some desire on Hamlet's part to protect his nation, don't you? One of the things he most admires about his father was his paternalistic attitude towards Denmark's citizenry.
Hamlet struggles between leaving his carefree life as an unencumbered university student and the weighty task of ruling his nation. He can hardly say no to the latter.
I don't think he wants the crown at all, but has too much moral integrity and love for his father to let it be assumed by Claudius.
There is always a choice, but I'm sure Hamlet hardly sees it that way. To choose to go against Claudius and Gertrude's demands would essentially be to deny who he is, the prince of Denmark. A prince does not generally disobey the orders of the king and queen, which is also why Hamlet probably feels like Denmark and even his own self is a prison because he feel so limited in his power of choice. I suppose he could turn and run away, go underground, become anonymous, but then he would have to leave behind the only life, home, and identity he has ever known. That's easier said than done and he probably just figures if he can work up the courage to avenge his father's death, he will most likely gain the crown and be set free from this prison he knows.