The term "rooted" refers to a color demarcation.
For instance, if you look at someone's hair who hasn't had their color touched up, i.e. a blonde with dark roots, you might see roots anywhere from 1/2 inch to 1 1/2 inches long.
This can actually look great. Coffee brown roots with pale copper looks really nice. There are a lot of attractive two-tone combinations.
If you have a wig that's pale enough to show a difference, you can simply stain the roots a little darker. It gives a lot of depth perception and makes it look more natural.
Thanks for the great question.