What role did monks play in advancing literature?
Monks kept the first books.
In the days of yore, the dark Middle Ages, books were only accessible to monks and priests because they were written in Latin. Only they can study and read. The common folk have no "education" hence the term "Dark Ages".
Because the monasteries have the books, the monks, in a way, preserved important literature. These literature were later transcribed in the common tongue thanks to the efforts of people (like Chaucer) who realized the importance of writing and communicating in the common folk's language rather than Latin.
Thus, the Middle Ages then slowly paved for the height of art and knowledge that we know as the Renaissance.