In modern power systems, Rate of Change of Frequency (ROCOF) is employed in monitoring and control applications. However, a standard approach towards ROCOF measurements is still missing. In this paper, we investigate the feasibility of Phasor Measurement Units (PMUs) deployment in ROCOF -based applications. For this analysis, we select three representative synchrophasor estimation algorithms and compare their accuracy in datasets inspired by real-world acquisitions. Based on the proposed results, PMUs prove to be accurate ROCOF meters, as long as the harmonic and inter-harmonic distortion within the measurement pass-band is reduced. In the presence of transient events, the synchrophasor model looses its appropriateness, as the signal energy spreads over the entire spectrum and cannot be approximated as a sequence of narrowband components. For these reasons, a re-definition of the IEEE Std. C37.118.1 requirements is recommended to suitably define ROCOF measurements based on real-world operating conditions.