SOLVED! The solution to the rotation issue is to call EntityItem#onUpdate manually, since it's not called automatically unless the entity is spawned in the world (and thus the age of the entity, which controls its rotation, doesn't get updated). The solution to the black-rendering issue is to use the setLightmapDisabled method instead of GlStateManager.disableLighting(), as there's apparently a texture map used for lighting when rendering, and that needs to be disabled to get a full-color render
I'm *not* doing anything with its rotation... and it's just not rotating at all...
As for the lighting, I *didn't* disable lighting at first, and it was black; that's why I tried disabling lighting, but it's still black. Either way I tried that, it still turns out black.
*EDIT* A little bit of debug output shows me that the age of the EntityItem is *not* ticking up. I'm going to look into that more, but I assume that's because it's not spawned in the world? At the same time, I don