Agent roll going super far?

so i've seen agents (operatives and snipers) do super far rolls sometimes in PvP and i'm wondering how this works? Usually its when they start the fight, they will do a roll, and as the ground under their feet dissapears, they roll super far in one go.

I've only have this happen once or twice myself, and i'm not sure whats causing it. Is it a certain distance you need to be in the air? or roll and jump or something?