"Personified" may not be the right term here. The fact that sin "enters" the world does not imply willfulness or personality on sin's part. It remains a passive object that has entered the world through the agency of Adam. The same may be said of death. So I would prefer "objectified" to "personified" in this case. Now to the meat of the matter:
Paul seems to use the term "sin" in Romans 5:12 to refer to a state of separation between humans and God, rather than "missing the mark" or violating the law of God. It may be helpful here to refer to Jewish concept of the "yetzer harah," with which Paul would almost certainly be familiar.
Traditionally, rabbinical thought considers the evil inclination to be part of God's creation that must be guided by God's law. Thus, lust (for example) is natural, but it is up to men to control it. God gave Adam and Eve the commandment and later gave the Torah to the Jews to enable them to lead a righteous life that would otherwise be impossible because of the yetzer harah. Sexual passion is a good thing expressed within marriage but not outside of it. The same may be said for other passions and tendencies that lead to sin. For example, rest is good; slothfulness is not. Anger against an evildoer is natural, but vengeance belongs to the Lord. Hunger is good because without it we would not eat, but gluttony is sinful.
Paul's teaching here is apparently an innovation in rabbinical thought. For him, the yetzer comes into being because of Adam's sin rather than Adam sinning due to his failure to control the yetzer.
Regarding death, Paul sees this as the result of sin. Romans 6:23:
For the wages of sin is death, but the gift of God is eternal life in
Christ Jesus our Lord.
Conclusion: Paul understands "sin" in this verse to be an inborn tendency to do evil, inherited by human kind because of Adam's fall. Death results from sin rather than being a natural part of life. Death and sin are objectified rather than personified in this passage. They enter through Adam's agency not their own.