Read it for yourself. God didn’t spare His own Son, and therefore will freely give us all things! (Romans 8:32) Paul declares that because God didn’t hesitate to do the hardest thing (to give His Son), He surely will do the comparatively easier thing (to give everything to those who place their trust in His Son).
It would be unthinkable to see God giving His Son… then backing out on our part… wouldn’t it?
It’s probably best to ask at this point, “What does He mean?” Does ‘all things’ guarantee a life of prosperity, comfort, and safety from the persecution of enemies maybe?
Probably not… considering a few verses later he cries, “For Your sake, we are killed all day long; We are accounted as sheep for the slaughter (Romans 8:36).”
Paul describes this as being brought about by tribulation, distress, peril, and the sword. Yet… he insists… at the cross, Jesus obtained all things for us.
Paul is declaring that God will give us all things that are good for us. He will give us everything we need to be conformed to the image of Christ, to bring glory to His name, and to acquire everlasting joy. Our real needs are met even when we don’t know what those real needs are.
He will do this when our greatest… our only need is His grace to deal with, well… whatever comes…
Paul is not declaring something unrealistic here. Christians will endure many of the same trials as the rest of the world… sometimes worse. But in tribulation, all those in Christ will be proven more than conquerors… we have been (and will be) given everything… everything we need to be like Jesus.