I think of it like a child asking a parent for candy. Sometimes, no matter how good you are, how much work you have done, and how entitled to something you think you are sometimes the wiser adult says “no” because he/she knows what is best for you. Or, instead of candy the youngster gets a heaping spoonful of vegetables.
The same goes for asking for things through the rosary. You can ask for anything, but God will only give give you what your truly need and in the manner He sees fit. It may not be the way you expect or even want, but His ways are not our ways. So while we may think some of our needs are truly great and pressing and deserving of all God’s attention, He knows better. I truly believe that God hears and answers all prayers, but we have to have faith and an open heart to accept His reply.
I wrote a little meditation about asking for miracles which is somewhat related: