How do I stop the player momentum when they fall from a platform?

Sorry for the bad English.

I'm doing a roll script for my game,but the problem is that when the player rolls off of a platform,because of the root.Velocity, the player flies off the platform.

that's the part of the roll script

elseif input.KeyCode == Enum.KeyCode.E and  humanoid:GetState() == Enum.HumanoidStateType.Running and debounce
		 or input.KeyCode == Enum.KeyCode.E and  humanoid:GetState() == Enum.HumanoidStateType.RunningNoPhysics and debounce then 
		debounce = false
		animTrackroll:Play()
		print "now"
		local Root = localPlayer.character:WaitForChild("HumanoidRootPart")
		Root.Velocity = Root.Velocity + Root.CFrame.lookVector*200
		if humanoid:GetState() == Enum.HumanoidStateType.Freefall then
			print "obby"
			Root.Velocity =  Root.CFrame.lookVector*-Root.Velocity
		end
		wait (0.2)
		CR = true
		wait(0.2)
		debounce = true
		CR = false
		
		end
end)

I tried cancelling the momentum when the player is freefalling,but I think the freefalling statetype only triggers if the player jumped. I wanted to know how to detect if the player falled from a plataform,and also if there's a better way to do a rolling script,than using the Cframe.