I did a VC for the adult version of the character a long time ago but at last I present the Young Roronoa Zoro!
He was first voiced in the Odex English dub of the One Piece anime. At the moment I'm not sure which VA is was so until I have some confirmation the clip will remain attached with "Unknown Voice Actor".
In the 4Kids English dub of the One Piece anime he was called Zolo and was voiced by Andrew Rannells.
In the Funimation English dub Young Zoro is voiced by Brina Palencia.
For the English version of the One Piece video game Unlimited Cruise he is voiced by Aaron Dismuke.
*Cynthia Cranz is credited as Young Zoro in episode 2 of the Funimation
dub but it was just grunts and yells in a flashback. There was no actual dialogue.