There is much evidence that three of those named were sons of Japheth: Magog, the second son of Japheth, settled in what is now known as Russia; Meshech, Japheth's sixth son, settled in what is now known as Armenia; and Tubal, Japheth's fifth son, settled in Cappadocia, or today's Turkey (Gen. 10:2). We know from Ezekiel 27:13 that both Meshech and Tubal were known for trading slaves. In fact, we get the word "slave" from the "from Medieval Latin sclavus, from Sclavus Slavic; from the frequent enslavement of Slavs in central Europe during the early Middle Ages" (http://www.merriam-webster.com/dictionary/slave?). Russians are ethnic Slavs.
However, Rosh is only mentioned once in the King James Version of the Bible, and unlike the other three, was not a son of Japheth, but was one of the twelve sons of Jacob: Benjamin (Gen. 46:21). The error of including Rosh in with the other three, stems from a mistranslation of the Hebrew word, "רֹאשׁ (ro'sh), meaning "the head, leader, or chief." Notice the actual wording of the text below.
"Son of man, set thy face against Gog, the land of Magog, the chief prince of Meshech and Tubal, and prophesy against him, and say, Thus saith the Lord GOD; Behold, I am against thee, O Gog, the chief prince of Meshech and Tubal" (Ezek. 38:2-3).
I believe that the Bible scholars, knowing that the land of Magog is modern day Russia, mistakenly interpret רֹאשׁ (ro'sh) as a noun (calling it "Russia," and even calling Meshech "Moscow"), rather than as the adjective describing Gog as the leader of the three nations: Magog, Meshech, and Tubal.
Say what you want about the King James Version, but I find it to be outstanding!