Also, for official sources etc. I believe I'll self-censor to use 'Rox' but I feel fairly strongly Oda wanted it to be 'Rocks'. I don't say this because I know about the character or have a confirmation on the character but because I know Oda's preferences when it comes to Japanese kana that he thinks sound cool/appropriate for shonen manga. Rocks gets that across. Rox is fine though! No qualms about it whatsoever!
Iirc, Japan tends to associate Rock with rock'n'roll and not the minerals. Hence Megaman's original name being Rockman.
Do you think that's what Oda is going for with this name, that we'll see something akin to Keith Richards in Pirates of the Caribbean?
On a personal note, I addhere to the Rox spellling because it makes reading somewhat easier since rocks is also a common noun.
The first time I read the chapter the name was translated as Locks and I first thought it was Hina's nickname, because of her powers, since she was with whom Lacroix was talking to.