Roller vs flat tappet is a different discussion than solid vs hydraulic. The number of times this gets blurred on the cummins discussion groups is mind blowing.I think the powerstrokes and duramax engines have roller lifters
Diesel pickups have gotten quieter in phases. Exhausts got quiet, which meant they seemed really rattly. So they went after the injectors, added pilot injections, and valvetrain noise. More insulation under the hood, etc. Now they are going after front drive noise. Solving one unpleasant noise leads them to the next.