This paper presents a comparative study of various methods of roughness quantification applied to rock fractures. The parameters which are discussed and used for comparing 7 types of rock and two failure mode are : arithmetic mean value, quadratic mean value (and standard deviation of peaks heights), JRC and estimations of the fractal dimension by the ruler method, the analogy to Koch curve, the variogram and the power spectral density analysis. Regarding the results obtained and the discussion about the accuracy of calculation, it is difficult to draw a firm conclusion to state the most convenient method for quantifying roughness or complexity of rock fractures because all the parameters could be significant depending on the aims of the quantification. Nevertheless, the statistical analysis of results allows to point 4 independent parameters which have significant meaning and variability for quantifying roughness or complexity of natural rock fractures.