I had an emg today, doctor found, chronic denervation in bilateral l5 nerve roots, does this explain my pain in both my legs and my back?

It sure does: Yes, it can be the reason for your back and leg pain.

Possible: Problems with the L5 roots can cause both back and leg pain. Confirming with EMG that the root has been affected is helpful but it might not be the only reason for your pain. Discussing these findings with your doctor in view of your overall symptoms and other tests is important.