My understanding is, (and I have a book on this subject, just have to find time to read it) that this was written in a period where pure monotheism was assumed by the Jews, and the natural presumption of this was that God was the source of everything--good and bad. The concept of an opposing "god" which accounted for all evil in the world springs up some time during the Persian period where the dualistic Zoroastrianism took root. http://en.wikipedia.org/wiki/Dualism
There are Christian shools of thought (Calvinism) that God is indeed sovereign and in control over everything in the universe--and this includes evil. That He ordains everything in the universe according to his sovereign purpose, citing Eph 1:11. They argue that if God permitted evil unwillingly, you have moved into dualism (where an evil power must be at least equal to God).
least equal to God)
The paradox that God is sovereign over mankind's evil choices, yet this does not absolve mankind of responsibility over such choices seems to be what Paul is trying to explain in Romans 9:19-21:
One of you will say to me: "Then why does God still blame us? For who resists his will?" But who are you, O man, to talk back to God? "Shall what is formed say to him who formed it, 'Why did you make me like this?' " [ h ] Does not the potter have the right to make out of the same lump of clay some pottery for noble purposes and some for common use?
Check out the context surrounding this.