I am going to get smoked for this, but I think he is making a huge mistake. I feel that Royce is exactly the kind of player that could come back and use that to move up in the draft. Players that come back and help themselves are typically the guys who have talent but need to refine some of their skills, exactly like Royce. I think if he came back, he could move up from top 20 to top 10, which would mean millions of more dollars for him over the next 5 years. Not only that, but he would spend a year being the darling of college basketball, which would be huge in building his brand (the Tebow effect), rather than being just another rookie in the NBA. That again could be worth millions to him in the future.
That being said, if his family is hurting financially and he doesn't want to see that anymore, I completely understand. If that isn't the case though, I really think he should come back.