We are only saved (by the life of Christ) when we confess the Lord Jesus, believe and call upon Him – Paul makes this abundantly clear later on in Romans, in chapter 10 verses 9, 10 and 13 – “if thou shalt confess and believe… thou shalt be saved…..with the mouth confession is made unto salvation….whoever shall call upon the name of the Lord shall be saved.” The same truth that you are saved when you believe (and not before) and that we are saved by grace through faith (which is the faith of Jesus Christ, a gift of God) can be seen from Mark 16:16, Acts 16:31, Heb 10:39, 1 Cor 15:2, Eph 2:8 and Gal 2:16. Romans 5:1 also does not say “all humans are justified by faith”. No, this idea is universalism, Romans 5:1 says “being justified by faith, we….” So this verse says “we” i.e. those Paul was writing to, believers, it does not say all, and it also says that we are justified by faith, so it is obvious that unbelievers (who do not have faith) are not justified, as we are justified by faith.
More to be written, come back later.