[tom the eldest]

There is free will in tolkien's work.melkor become evil is out of his own free will.sauron also became evil out of free will.melkor rebel because he want eru to create life in the void,which eru didnt do.he also try to find the flame imperishable,which fail because the flame is with eru himself.also he corrupt the music of creation,and although this fail it still create evil in every creation in arda.he done that out of free will


EDIT:about the orc,the has free will,but they have limited use.for example,they are allowed to eat and drink but were not allowed to disobey or defy his master.about the balrog,they have free will,but they still under strict order from gothmog and morgoth himself.and so have free will but saw limited use of it.once they master have been defeated however,they are free from the orders and able to do anything they like.