Interesting, I am just going from throttle body's to rollers due to low speed drivability issue. Lack of control from idle to 2500 / 3000 - its either on or off. Rollers on my other car are far more progressive and controllable. Both engines are the same spec - 1800 VVC running the mems ignition ECU. The original tune was with the rollers. Looking at the throttle opening it can be seen that the area around the butterfly's is greater and less progressive than the orifice on the rollers. I think which ever way you go, the end result will depend on the vehicle/engine spec. and set up / tune. It will be very difficult to quantify whether you made the right decision.