Appreciate this is a pedantic query, but on the basis that the ball must be ON the touch line when a kick-in is taken and the touchline forms part of the playing area, as soon as the ball clearly moves it is within the field of play.  Therefore, if the player taking the kick-in mistakenly kicks/rolls the ball completely out of play, rather than fully onto the pitch, the ball must be deemed to have been on the field of play, albeit very briefly and only partially (the ball is only out of play when the whole ball goes over the touchline).

If this is the case, should the kick-in/roll-in be retaken by the opposition?