These rockers are better known as 'roller tipped' & are very good. They remove, or at least reduce the side load on the valve stems & the alloy body reduces the inertia, thereby allowing higher RPM without stiffer springs, but..........................

True roller rockers, the ones with roller bearings on the shaft are the best of them all. The Yella Terra brand ones that are made here in Australia do not have colour anodising as this [allegedly] reduces the strength of the alloy & they come as a complete rocker assembly with a higher lift ratio of 1.54 to 1 compared to the 1.44 to 1 of the standard rocker arms.

These are Ferals rockers, & it's a good shot showing the whole kit.