Rotational Stokes emission is generated by focusing a linearly-polarized femtosecond pump beam into molecular hydrogen with a supercontinuum, which occurs by self phase modulation as a result of passing the beam through molecular nitrogen. The supercontinuum acts as a seed beam in the generation of rotational Stokes emission. However, enhancement of the supercontinuum by increasing the peak power suppresses the generation of the rotational Raman emission, due to a large gain for the supercontinuum and to the poor beam focusing capability of the pump beam, probably as a result of self focusing.