Why this is wrong is;In Romans 8, the context demands that those whom God foreknew is the family of Abraham, Isaac, and Jacob with whom he had made a covenant of works, the Mosaic covenant. This is pictured as bondage for Israel as they labored under it. He has a whole chapter, chapter 7, detailing the frustration of a Jewish man who is attempting to please God by keeping the law only to have the perfection of the law condemn him.
However the answer to the frustration is given in chapter 8 where the perfection of the law and the righteousness thereof is realized in Jesus Christ and his righteousness imputed to them in the person of his Spirit. Israel is admonished to walk not after the flesh (trying to keep the law of Moses by the power of the flesh) but after the Spirit. (who we find out later in the chapter indwells the believer in Jesus). We find out in chapter 8 that those of Israel that are freed from the law by being "in Jesus Christ" are also made sons of God by that transaction. Walking in the Spirit is submitting to the Lordship of Jesus Christ and allow him to lead and direct their paths. Now the Fatherhood of God and a new family is far better that the fatherhood of Abraham.
Now, while there are some universal truths in the chapter that can and will apply to gentiles, there are some things that cannot apply. The universal truths that apply to gentiles will be stated also in passages where the gentiles are being addressed. The primary audience that Paul has in mind from Rom 7:1 through Rom 11:12 is Israel. This is the reason foreknowledge is not found in passages that are written to gentiles, like the letter to the Ephesians and the one to Colossians although some of the other doctrinal terms are.
Therefore "foreknowledge" means known before and applies to his people Israel who he has known before when they were under the operative principle of divine dealing of the Mosaic law. He certainly did not know the gentiles before. I am not guessing about that because it is plainly stated. One can read it for himself for confirmation of this truth.
Eph 2:11 Wherefore remember, that ye [being] in time past Gentiles in the flesh, who are called Uncircumcision by that which is called the Circumcision in the flesh made by hands;
12 That at that time ye were without Christ, being aliens from the commonwealth of Israel, and strangers from the covenants of promise, having no hope, and without God in the world:
13 But now in Christ Jesus ye who sometimes were far off are made nigh by the blood of Christ.
Romans was written in 58 AD and Ephesians was written in 60 AD. In time past there was no plan revealed for gentile salvation.
Think about this.
6 Not as though the word of God hath taken none effect. For they are not all Israel, which are of Israel:
7 Neither, because they are the seed of Abraham, are they all children: but, In Isaac shall thy seed be called.
8 That is, They which are the children of the flesh, these are not the children of God: but the children of the promise are counted for the seed
24 Even us, whom he hath called, not of the Jews only, but also of the Gentiles?
25 As he saith also in Osee, I will call them my people, which were not my people; and her beloved, which was not beloved.
26 And it shall come to pass, that in the place where it was said unto them, Ye are not my people; there shall they be called the children of the living God.
30 What shall we say then? That the Gentiles, which followed not after righteousness, have attained to righteousness, even the righteousness which is of faith.