The correct romanization for the character would be Rintaro
u Okabe (Source:
http://steinsgate.tv/character/index.html).
However, in the recent official English release of the game they romanized it as Rintaro Okabe (Source:
http://steins-gate.us/characters.html, I've checked in the actual game too to be sure it wasn't just an error in the website).
Which one should we use? I left it as Rintaro for the time being.