Roose killed Robb in the same way — making his death a sweet moment of revenge.
The close embrace combined with a stab and twist is a brutal way to go. But Roose pulled this exact move on Robb Stark. As rough as it may have been for viewers to see Ramsay take more power, there was a glimmer of vengeance in the scene. Roose even fell to his knees and then backward onto the floor in the exact same way as Robb did back in season three.