red always fades so that would be ok, other colours wont though, not so you wont get roots anyway but if you have fine weaves/slices of colour, the re-growth doesnt show half as much anyway. If its subtle enough it really wont be a problem. Have a word with your hairdresser.
I had red flashes in my hair but i had them done underneath the top layer of hair so there was no re-growth to see. It was all underneath. It looked great too!