According to Deadline, Joe Naufahu (Spartacus: Vengeance, The Last Saint, The Kick, Go Girls) has booked a recurring gig on season 6 of Game O Thrones.
The site doesn't have any specifics on who he'll be playing, but there's a decent chance he's been cast in one of the new Dothraki roles. In the season 5 finale, Dany find herself surrounded by a khalasar so there's bound to be a few characters from that group emerging as more prominent players. Could Naufahu be Khal Jhaqo, perhaps? We'll update as soon as we know more.
Game Of Thrones will return next April.