as far as the cold weather shoock i have no clue, if the roots and medium ended up frozen solid they me be done, canabis can handle a frost or 10 as long as the medium dosent freeze.
if things start looking really bad try and clone the whole plant if you cut it at the stem and put it under a humidity dome in some water it should perk right back up. i dont have much experience cloning an entire plant but i do know the lower part of the plant contains more hormones that are used in root development than the top of the plant so it might take to root fairly fast depending on how big this plant is.
some pics would be great and some details on how badly it was stressed.