The X-rays emitted by a rubidium plasma source created by the PHELIX laser at an intensity of about 6×1014 W/cm2 were studied. The lines have been measured using Bragg crystals in the wavelength range between 3.8 and 7.3 Å and identified by means of a numerical method developed to describe highly charged rubidium ions in LTE plasma. The experimental plasma temperature, density and charge state distributions have been estimated using non-LTE codes such as CHIVAS and AVERROES. The LTE plasma temperature and density used in the calculations are those allowing to reproduce the calculated NLTE charge state distribution. In order to optimize the use of computational resources, a criterion is established to select the configurations contributing most to the spectra among all those obtained in detailed level accounting based on the MCDF code. Seventy Rb X-rays have been identified among which forty-nine are reported for the first time. The capabilities of our method are demonstrated by the good agreement of our identifications with previously published data when available.