Harvest the plant when the trichomes say it's time...
Leaving the roots attached isn't going to make any more THC get to the buds. The roots contain no THC.
I think you'll find that the buds will dry more quickly & efficiently if you cut the branches off and hang each one individually, with plenty of air circulation blowing around them.
Proper drying & curing to get that wonderful smell/taste takes time.. A week or more of air drying and a month or more of curing in jars will have you very happy with the result.