How rough it is depends on alot of different factors, but normally spring rate and damper valving is the main cause.
That is one of the main concerns for the MeisterR Zeta-R coilovers is that they have to be compliant over uneven fast road surfaces.
Normally, a harsh or a rough suspension are one that are design for flat track surface but driven on uneven roads.
Another good thing about the Zeta-R is that it is a dual perch coilovers.
This give a few advantage over a single perch coilovers / springs&damper combo.
1. You can lower the car without disturbing the springs preload (tension), which mean you can more control over the car as lowering the car will not affect any moving part of the suspensions.
2. Lowering the car does not reduce damper stroke travel. This is important as you want as much damper travel as you can in a car that will be driven on uneven road surface to avoid bottoming out the damper and hitting the bump stop.
You have to decide what you want and get the suspension that are designed for that purpose.
Alot of expensive Japanese suspension actually perform worst on uneven road than standard suspension simply because it is way too hard for street use.