It looks like you are having quite a few problems, so where to start first?
You have no main method....
DiceRoll has no type associated with it.....
You have no real constructor for your class....
die1 and die2 have no types associated with them.....
NUM_SIDES is not initialized to anything.....
It would be really helpful to see the all of your code, otherwise we are just making assumptions about what you do and do not know how to do.