Paul explicitly tells us exactly what he's talking about in Romans 9-11.

We don't have to interpret.
We don't have to exegete.
We just have to look at the text and read it.

Romans 11:25 "For I do not want you, brethren, to be uninformed of this mystery—so that you will not be wise in your own estimation—that a partial hardening has happened to Israel until the fullness of the Gentiles has come in."

That's what he's talking about. He's not talking about the eternal destiny of everyone at the end of time. He's talking about a partial and temporary hardening that has come upon some Israelites in the midst of history so that more Gentiles can be grafted into the covenant community.

And so he has to answer the obvious objection: "If Israel is God's chosen people, then how can Gentiles be brought into the covenant community before some Israelites?" This is the same conflict that we see coming up in the Gospels and in the Book of Acts. The confusion that Gentiles would become part of the true covenant community before some Israelites.

But Paul explicitly states that those Israelites who are temporarily hardened are not marked for eternal damnation. They can be grafted into their own tree if they do not continue in unbelief. That is exactly what he says. - Timothy Renfro