I am going to present an argument that Romans 9; 20-23 is not about God's treatment of individuals but is rather about his treatment of national Israel. I claim thiat this is relevant to the matter at hand since, if the argument works, it undermines the claim that Romans 9 asserts that God can "blame" individual people who are "pre-destined" to loss.
Romans 9 is about how God has been faithful to the covenant with national Israel and, more specifically, the "potter's account" in verses 20 - 23 is Paul's explanation of how God "has the right" to use national Israel for a specific purpose in his redemptive plans. It has nothing to do with matters of individual persons being elected to receive or not receive faith.
The fact that Romans 9 and 10 is all about the covenant with national Israel is clear and I suggest that the evidence for this is overwheming. I shall return to this. In a context where Paul is clearly explaining things about national Israel, it makes no sense to have him suddenly go off on a tangent and make theological statements about individuals being pre-destined to saving faith (whether Jew or Gentile or whatever).
What has Paul been talking about just prior to his giving the potter account? He has been talking about a hardening - the hardening of Pharoah. Why has Pharoah been hardened? To effect a great act of redemption of God's part - the deliverance of the Hebrews out of Egypt. It then follows that Paul's giving of the potter's account should also address a hardening that takes place in order to effect great redemptive purpose. Who is being hardened? Israel is being hardened. What is the great redemptive act? - accumulating the sin of the world onto national Israel so that it can then be transferred onto her Messiah. I will provide arguments for all this in other posts.
Now back to Romans 9 (and 10) being all about the covenant: Note the following from Romans 10:
"But the righteousness that is by faith says: "Do not say in your heart, 'Who will ascend into heaven?'" (that is, to bring Christ down)"or 'Who will descend into the deep?'" (that is, to bring Christ up from the dead). 8But what does it say? "The word is near you; it is in your mouth and in your heart,"that is, the word of faith we are proclaiming."
Now consider the following from Deuteronomy 30:
It is not up in heaven, so that you have to ask, "Who will ascend into heaven to get it and proclaim it to us so we may obey it?" Nor is it beyond the sea, so that you have to ask, "Who will cross the sea to get it and proclaim it to us so we may obey it?" No, the word is very near you; it is in your mouth and in your heart so you may obey it.
Is anyone going to deny that Paul is "transcribing" from this text in Deuteronomy. But what is Deuteronomy 30 all about?
It is about covenant renewal. Starting at verse 1 we have
When all these blessings and curses I have set before you come upon you and you take them to heart wherever the LORD your God disperses you among the nations, 2 and when you and your children return to the LORD your God and obey him with all your heart and with all your soul according to everything I command you today, 3 then the LORD your God will restore your fortunes [a] and have compassion on you and gather you again from all the nations where he scattered you.
This clear reference to the covenant - and specifically the element of covenant renewal - comes at the end of a retelling of the covennat story that begins in Romans 9. Its all there - Abraham, Isaac, Jacob, Moses and the disobedience of the people to the covenant, exile, and here in this text - covenant renewal.
If you come to Romans 9 wanting it to affirm a belief that you bring to the text about individuals being predestined, you can always come to vv 20-23 and claim that your belief is supported. But you do so at the price of ignoring a powerful body of evidence that shows this material is about the "election" of Israel. If one ignores context, almost any position can be argued for.