Hi
Extracting DNA from rootless hair is a new technique.
It has not, as yet as far as I am aware, been accepted as definitive by the Courts as a DNA Sample due to the risk of contamination.
A hair with roots is good evidence.
AFAIA, DNA extracted from a hair is mitochondrial DNA which is the maternal side of your genome. DNA extracted from a hair root, on the other hand, has the DNA from both sides of your genome and is much better for identification purposes.