Roy would play those guys all year long in an effort to bring them along. K sits them on his bench and cries crocodile tears about how short his bench is. Yes, it is short. But part of that lack of depth is totally voluntary.
The rest of the duke bench isn't that great at all. The fact Roy would play the slackers, and K doesn't risk playing the slackers, shows why K has dominated Roy of late. Roy coaches like its a youth league, and he needs to make sure everyone on his bench gets their minutes and stays happy and engaged. K coaches like it's a slate of games that he wants to win, so he plays the players that will enable him to do so.