How does Roland die in Unwind by Neal Shusterman?

Roland only dies if you believe unwinding actually results in death. The "Bill of Life" that appears in the very beginning of the book states the following about unwinding:  

However, between the ages of thirteen and eighteen, a parent may choose to retroactively "abort" a child . . . on the condition that the child's life doesn't "technically" end.

Many people in the society absolutely believe unwinding a child does not end that child's life, including a child, who says,

I was never going to amount to much anyway, but now, statistically speaking, there's a better chance that some part of me will go on to greatness somewhere in the world. I'd rather be partly great than entirely useless.

If you believe unwinding actually ends the life of the child, then Roland dies by being unwound toward the end of the book at the harvest camp where he, Connor, Lev, and Risa stayed.  
The clappers destroy a great deal of that harvest camp, and Connor's arm is injured so badly that it can't be saved. Without Connor's knowledge, he is given the arm of an Unwind. The arm he is given is Roland's arm, so perhaps Roland is still not entirely dead.