Most likely, it's hiring someone for Isiah to delegate tasks to if he's going to be wearing both a coach's and GM's hat this year. Because all Isiah/Knicks smartassery aside for a second, doing both jobs at the same time is a hard thing to pull off.
The tweets I saw (IIRC) were two years/$10 million. In a league where Omer Asik is going to get $8 mil/year, that is absolutely NOT overpaying for a guy like Roy. If he can play 6th-man minutes, I think it's a great deal.