Taxi on rough runways is a certification requirement for transport category aircraft. The criteria is "the roughest ground that may reasonably be expected in normal operation". You can check FAA advisory circular AC25.491-1 for details on what is done to certify aircraft for these conditions. One of the standards for this was the so-called San Francisco runway, which was apparently quite rough until it was re-paved... but I know some manufacturers have taken to using roughness data from a runway in Russia, although I don't know which one exactly. Flight data recorders may not be totally accurate for quantifying runway roughness, as many of the dedicated FDR accelerometers installed on aircraft attenuate frequency content above 4 Hz.