Romans 9 kicks off with Paul asking the question of God's faithfulness to Israel, highlighting that not all descendants of Abraham are “true” members of God's people. Which brings up the hardening of hearts question, which then leads to the theories about divine justice and free will. 
The beauty of His word is that the whole bible tells us His nature, so when we reference scriptures like 1 Timothy 2:4-5 and John 3:17 we know that God’s desire is that ALL will be saved. 
 

Romans 10 highlights the importance of proclaiming the gospel, 
“ faith comes from hearing the message of Christ”. 
Paul insists that anyone who believes in Jesus will be saved, and as believers, our goal is to get that message out!
 

Lastly Romans 11, he clarifies that God has not rejected Israel; their unbelief opens the door for ALL. The covenant with Abraham was for all nations, and God's plan always included reaching Gentiles while ultimately restoring Israel. 
Paul emphasises that salvation is by grace, not works. He reminds us never to become self righteous or prideful, but to remain thankful to be grafted into God's family. 

He concludes with a promise that Israel will eventually be brought back, fulfilling God’s covenant of forgiveness.