Aphelion, what color did you ask for when you ordered? My concern is that if the wig was dyed with Rit Dye, you may get unexpected color results. Maybe you can dye the wig in a color that is closer to the color you asked for, but I'd do a strand test first.
Regarding protecting the silk, you can try using a hair dye fabric protector on top of the silk, but make sure you use a small brush at the roots when applying the dye, like a root applicator that comes with hair dye root kits. In this way, you can more carefully dye the roots without getting dye on the silk.
Edited by chatnoir - Jun 24 2013 at 3:24pm