EDIT: My definition of free will: That a conscious being can make a physical choice, and then have that choice being acted out in the physical world as he predicts it will.
I go in the opposite direction and say that we must have determinism for "free will" to work.
If free will is an emergent property, a sort of illusion in the mind, created from physical properties, then if indeterminism didn't exist, we could never truly make a choice.
We would lose all our free will to randomness, instead of having a preset course of events that we can choose from.
Imagine that you have a system so complex, that no conscious being inside of it can ever comprehend it fully, then imagine that consciousness is an emergent property (weakly emergent mind you) of the physical mass.
If that mass is deterministic, then each choice made in the mass by the weakly emergent consciousness, would be too complex too comprehend from within the consciousness when the choice was made.
While if we have a state of indeterminism, our free will would be taken.
Because if the mass was indeterministic, and we wanted to make a choice, then the mass might go against our will, and do something random, and we wouldn't want that.
Also about moral responsbility; we are fully aware of our choices, on a conscious level, if I want to kill someone, I'm fully aware of the damage being done as such I have a personal responsibility to take that responsibility.
If we didn't have a conscious experience that thought us the damage being done, then I agree we would not have responsibility for our actions.
But seeing as we do..