You got Mortz and KK the wrong way around.
In all honesty I think KK does have game but he is very stupid at the moment but that may change with experience. His kicking game is OK, his long passing game is non-existent but his short passing game and running game is his best asset but unfortunately he is inconstant also he is a good support player.
I still think Roberts in 10 times the player Mortz is but both will struggle without a halfback, Roberts passing and kicking game is far superior and his running game is probably more effective because he breaks tackles with his strength as well but he isn't as nippy. His supports play isn't anywhere near as good but that what fullbacks are for.
Is Roberts takes a backseat to Sandow he will probably flourish because he will have guys like Tonga, Hayne and Matuia to play to. I think Robert will be due for a big season with him and sandow being among the best players for out team next year.
KK is a faster version of Morts