I have bought this color rub so I can hide my roots, until I decide if I'll bleach them at home or at a hairdresser salon :D but it's meant for temporary highlights. Even though it's temporary you still have to be careful, if your hair is bleached or overprocessed the color may grab.
I like it a lot, it's very easy to use, and I'll probably try it once for highlights, even though it's a little bit irritating, because you have to be very careful where you lean and everything, cause it stains a lot of course :D
So about covering your roots with this...I can say that it's the best solution I've found. You can still see the roots a little bit, but it looks better :) Scroll down to see the pictures