A computational and experimental study of the optical propagation of light in a collisionally broadened three-level Raman amplifier is presented. The Stokes light consists of two distinct spectral components: of resonance stimulated Raman scattering (SRS) and on-resonance stimulated fluorescence (ASE). The intensity dependence of these effects on the buffer gas and on the intensity and detuning of the exciting radiation are calculated. We have carried out the calculation over physically realistic propagation distance. The theoretical model for a description of ASE i SRS signals generation in such a system was developed. The numerical calculations based on the rate equations agree with the experimental results.