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We present results of the analysis of 112 X-ray-selected and fully optically-identified quasars in four sky fields in the southern hemisphere, detected by the Rosat Position Sensitive Proportional Counters. These fields were originally studied for the ultraviolet-excess properties of objects in the fields. This is one of the largest sets of fully-identified Rosat-observed quasars.
We determine the quasars' power-law spectral index $\alpha_E$ with three different methods: spectral ``stacking'', hardness ratios, and direct fitting, and discuss the differences between each of these methods. We derive monochromatic X-ray and optical luminosities $\rm L_x$ and $\rm L_{opt}$ and discuss the relationship between them, examine the optical-X-ray spectral slope $\alpha_{\rm ox}$ and the related $\rm L_x/L_{opt}$ ratio and their relationship to redshift, $\rm L_x$, and $\rm L_{opt}$, and finally present a model which could explain the observations.
