This white cockroach is not an albino, I just happened to find it shortly after molting. Because insects have a hard exoskeleton on the outside, they need to shed that exoskeleton to grow. The process is called molting, and when they emerge from their old exoskeleton they are soft until the new exoskeleton has time to expand and harden. (They are just like soft-shell crabs, which are soft because they recently molted.) Insects are often lighter in color for a brief period after molting.
Of course, insects are very vulnerable after molting, because their protective exoskeleton is not so protective. In this case, ants were taking advantage of the situation to attack the cockroach.