OSX disable wake on USB
From a quick google it seems you are out of luck.

The basic reasoning is that you (normally) would want to wake from key or mouse press, and if these are connected via USB then the mac needs to detect activity on the USB, and rather than distinguish between clicks and movements it wakes on both.

Most of apples own mice are bluetooth, and mac os x has an option within the system preferences not to wake mac on bluetooth (either disable on move and click or just movement, I forget which). 

Can you pull out the trackball's ball?  Turn it upside down, or you might just have to disconnect it.  

Good luck!