The Jewish believers in Rome would have known the Old Testament reference on which these verses are based (Deuteronomy 30:11-14).  Paul explained that Jesus Christ is the ultimate ‘Word of God’ and righteousness comes through believing and obeying Him. The first steps in obeying Jesus Christ are to believe that He is God's anointed Saviour (John 6:28-29) and then be willing to tell others.

In our minds and hearts, we believe all sorts of things.  But it is not until we tell others what we believe that our faith becomes identifiable to others and to God.  Of course, in some circumstances, admitting that you believe in Jesus Christ is very dangerous: and there are probably millions of secret disciples around the world today.  But believing in Jesus was never designed to be secret.  People may observe our changed lifestyle, but will never understand how it has come about unless we tell them that Jesus has changed us and can change them too.  

That is why Peter writes to Christians who are being persecuted, telling them to "... in your hearts set apart Christ as Lord. Always be prepared to give an answer to everyone who asks you to give the reason for the hope that you have. But do this with gentleness and respect" (1 Peter 3:15).

Confessing that Jesus Christ is Lord takes our faith into the real world.  No unbeliever can say it.  Yet many believers are reluctant to be open about Jesus.  Why is this?  It is because of fear.  Fear that others will reject us; fear that we are unworthy; fear that we will not know how to answer people's questions or fear that such a confession will set new high standards for our behaviour in the future.  All these fears are encouraged by the devil, but we need to remember "There is no fear in love. But perfect love drives out fear ..." (1 John 4:18).  So do not be afraid to speak about Jesus as your Saviour and Lord of all.