I studied Hamlet/Ros and Guil last year... woo, i loved it! you have to focus on contexts shaping values, hence the 2 plays have different views on common issues, or they foreground different issues.
just briefly...
context of hamlet--
christian context, elizabethan period, renaissance, shakespeare was a social conformist, ie he reinforced the social hierarchy of the time, marginalisation of women, monarchy, but he did question classical Humanism and was influenced by skeptical philosopher Montaigne.
context of R+G--
satire boom, theatre of the absurd, existentialism, emergence of postmodernism.
also look at genre:
Hamlet is a revenge tragedy- a male of noble birth brings about the destruction of himself, who must die in the end, because revenge is wrong after all. rev trag assures that there is order and reasoning in the world, which parallels renaissance values
ros/guil is a postmodern play influenced by existentialism and absurdist theatre. absurdism offers an existentialist view of the outside world where there is no true order of meaning, no plot but a series of free floating images. protagonists ros and guil have no control over what happens and are ready to walk off the stage because nothing really happens. so this reflects the contemporary idea that everything has been said and done, has brought about destruction in the 20th century (2 world wars amongst other things) showing stoppards rejection of reasoning and fate. so what you really have in ros and guil is a set of questions...
you'll notice that there are issues that both texts deal with, such as death, "nature", the role of language, but have contrasting values communicated, while there are issues left out by stoppard showing a change in whats relevant due to a shift in context, such as the issue of kingship, and the great individual, which stoppard "challenges" or questions, by having 2 marginalised characters centred, etc.
argh this is kinda long