The wispy shots are probably evidence of how badly damaged the root system was: they don't have the capacity to put out the size shoots you were expecting. You can prune out whatever you don't like whenever you want, but it is unlikely to promote larger growth.

Thanks Kudzu9, Will the roots recover with time to start producing larger stalks?

Yes...it will just take some time. Keep watering it regularly and it will recover and get back to the sizing you expect.

depending on how cold it was and how much sun it gets, it will recover slowly however it probably will not grow to its full size.

I'm assuming mulching would help protect the roots from the cold. We are zone 6b here in the mountains of NC, but the last two winters has made it seem like a zone 5. Both winters saw -3 degrees which is lower than anything in the twenty three years we've been here. The first three years we had the bamboo we saw a few temps in the +6 degree range, which is normal, and the they held up very well. So evidently that 9 degree drop made all the difference. Perhaps the mulch will give some protection from that 9 degrees if it occurs again.