[To the best of my understanding, and with the help of the wise counsel here at BH (regarding grammar and additional textual information, although each contributor has independently arrived at a different interpretation) I am answering this question outside of the normal bias because otherwise a centuries-old interpretive focus on faith continues unchallenged instead of a focus on Christ (who is Faith, the only Evidence of things not seen, the only Substance of things hoped for).]
ANSWER
This is not figurative language in Romans 10:6-8. It is, instead, spiritually literal language. How so? Simply put, Paul's messages always point to Christ.
When Paul speaks of love, hope, justification, salvation, righteousness, faith, etc --he is pointing to Christ.
Paul clearly points to Christ again here in this message (through inspiration), clarifying OT truth by incorporating NT truth to enlarge the previous understanding of his audience.
There is nothing here that uses figurative methods from literature, but it is all spiritually literal. This is a main salvific message from God Himself! Paul is revealing a message from Christ, the Righteousness which is of Faith, who is actually the One speaking through Paul.
The Lord our Righteousness is speaking through this NT passage and also through the quoted OT passage. In addition (unfortunately, due to the translators' systemic theology) He is referred to as "it".
Thus, I submit for everyone's further consideration and remembrance the following:
...and this is his name whereby he shall be called, THE LORD OUR RIGHTEOUSNESS. (Jer 23:6b)
Jesus Christ is the only "righteousness which is of faith". And, He speaketh still.
6 But the righteousness which is of faith (the Lord our Righteousness) speaketh on this wise
8 But what saith it (He)?
[Italics mine]
Here is the message from the Lord our Righteousness, the same One who is the Righteousness which is of Faith:
Say not in thine heart, Who shall ascend into heaven? (that is, to bring Christ down from above:) Or, Who shall descend into the deep? (that is, to bring up Christ again from the dead.) The word is nigh thee, even in thy mouth, and in thy heart: that is, the word of faith, which we preach; That if thou shalt confess with thy mouth the Lord Jesus, and shalt believe in thine heart that God hath raised him from the dead, thou shalt be saved. For with the heart man believeth unto righteousness; and with the mouth confession is made unto salvation.