Answer
Romans 9:5 is a Scriptural evidence to the fact that Jesus Christ is the only true God just as His Father is the only true God.
Nowhere is a son different from his father in nature and attributes.
Explanation
In this modern age we have easy access to the original sources of the Scripture in both Hebrew and Greek.
Let us study the original Greek of Romans 9:3-5:
“kinsmen of me according to flesh
Who are Israelites
Whose the divine adoption as sons and the glory and the covenants and
the lawgiving and the service and the promises
Whose the patriarchs and
From whom Christ according to the flesh
the being (who is) over all God blessed to the ages Amen”.
In proper English, the above can be rephrased as:
“my relatives, according to the flesh, who are Israelites, whose is
the adoption, and the glory, and the covenants, and the lawgiving, and
the service, and the promises, whose are the fathers, and of whom is
the Christ, according to the flesh, who is God over all, blessed for
all ages. Amen”.
Why RSV is Wrong
According to RSV, the last sentence reads like this:
“God who is over all be blessed for ever. Amen”.
In this, the verb “be” is added by the translators but is not in the Greek original.
The lack of a finite verb shows that the above is not a sentence or a clause. It is only a phrase and a phrase can never stand on its own!
A phrase is always a part of another sentence/clause.
Yet the RSV keeps it as a separate sentence.
The Greek has the last part as, “the being over all God blessed to the ages Amen”. In this, the word “blessed” is not a verb but an adjective. There are no verbs in here. So this is part of the previous sentence/clause.
[This is very important because in a previous train of thought, Paul does not bring in another thought abruptly without a proper verb. That is, Paul does not abuse a doxology improperly and out of place.]
Why NRSV Corrected
The same verse is corrected in the New RSV in 1989. There it reads:
“and from them, according to the flesh, comes the Messiah, who is over
all, God blessed forever. Amen” (biblia.com/books/nrsv/Ro9.5).
Now, the verb “be” is absent!
Now, “God blessed for ever” is a phrase that does not stand alone. It needs to stand together with the previous clause.
So the actual verse is:
“comes the Christ who is God over all blessed for ever, Amen”.
The rendering is unmistakable.
God-blessed?!
I couldn’t find such a phrase in the entire Bible! “God is blessed” or “God be blessed” or “blessed by God” or “God blessed them” etc are found in the Scripture.
But never have I come across a place where the term “God” is used as part of an adjective such as ‘someone is God-blessed”. Never. May be an oversight from my side? Then someone can correct me.
Conclusion
Notwithstanding the personal “prejudices” of the translators, the Greek Scripture strongly points to Jesus as “the Christ who is God over all blessed for ever”.
If Jesus is the “monogenes” Son of the only true God, by default, He has to be the same kind, that is, the only true God because a Son cannot be of a different nature than His Father**(*)**!
Otherwise, He will be an illegitimate Son!
[(*) However, we know that the son of John (YHWH) cannot be John (YHWH) himself. But, the son of a human being (God) is definitely a human being (God).]