Unlike the trial procedures, a reliable characterization of the vertical turbulence distribution on a site should be based in unbiased statistical sample criteria. The sample size is as important as the criteria under which it is taken. We present here the statistical results of the optical turbulence profiles at the Roque de los Muchachos Observatory (La Palma, Canary Islands) over annual periods (2004 and 2005), as well as the developed instrumentation to fulfil the established criteria. The data were obtained using the generalized-SCIDAR technique at the Jacobus Kapteyn Telescope, and the campaigns were done monthly. In order to extend the statistics of the profiles to other important parameters for Adaptive Optics systems, we show the monthly average behavior of the profiles, studying the seasonal variation of the vertical distribution of the turbulence.