Everyone is entitled to their opinion, but from an engineering perspective, a PROPERLY DESIGNED roller rocker will have a constant ratio. The effective fulcrum length does not change. But, good luck finding an off the shelf rocker that is properly designed. The only way to get that is a custom rocker. If the pushrod side is not designed with proper valve side geometry in mind, then the ratios will not necessarily be constant because the lobe lift inputs will be inaccurate and skew the results at the valve.