normally root joint is just the root joint, it's purpose is to seclect skeleton hierarchy ... (when i rig)
i usually place a join right above the root joing in order to create spline handle ik to control upper body to the joint between shoulders.
but the root (when i rig) all the weight is set to 0) and i usually put the selection handle behind or in front so i can just select entire skeleton.
and to mproperly deform the hips, u have to add 1 or 2 hip joints on each side. .
hope this helped