I have since learned this is an interesting and complex issue. I will get back to you after dong some more research. In the interim I'd like to show you some context for the verse you quoted.
"What then shall we say? Is God unjust? Not at all! For he says to Moses,
“I will have mercy on whom I have mercy,
and I will have compassion on whom I have compassion.”
It does not, therefore, depend on human desire or effort, but on God’s mercy. For Scripture says to Pharaoh: “I raised you up for this very purpose, that I might display my power in you and that my name might be proclaimed in all the earth.” Therefore God has mercy on whom he wants to have mercy, and he hardens whom he wants to harden.
One of you will say to me: “Then why does God still blame us? For who is able to resist his will?” But who are you, a human being, to talk back to God? “Shall what is formed say to the one who formed it, ‘Why did you make me like this?’” Does not the potter have the right to make out of the same lump of clay some pottery for special purposes and some for common use?
What if God, although choosing to show his wrath and make his power known, bore with great patience the objects of his wrath—prepared for destruction? What if he did this to make the riches of his glory known to the objects of his mercy, whom he prepared in advance for glory— even us, whom he also called, not only from the Jews but also from the Gentiles?" Romans 9:14-24
Keep in mind that 1) the Pharaoh was no innocent victim, 2) People still have the ability to choose 3) Yet those who God chooses to have mercy on aren't chosen because they're the strongest, or the best-looking, or the least physically attractive, black, white - if there's any deciding factor it's character, and even then God can shape good character in people who lack it. 4) God know the future, so He knows in advance whose going to accept and reject Him and factor in the choices.