Spectacular progress in the observational study of rapidly oscillating Ap (roAp) stars has been achieved by considering high time- and spectral-resolution spectroscopy in addition to the classical high-speed photometric measurements. Such observations led to the discovery of a multitude of unexpected phenomena, generally pointing to an extreme vertical chemical non-uniformity of the atmospheres of magnetic CP stars. A detailed analysis of spectroscopic pulsational behaviour allows us to establish a relationship between pulsations and the vertical stratification of the chemical elements. This has become possible with the use of a Very Large Telescope on relatively bright stars. Using Extremely Large Telescopes promises farther heights for asteroseismology.