Modelling a power supply system
I need to find the net resistance of the load model which I have
  derived to be (R*jωL)/(R+jωL). However I do not know how to proceed.


Multiply top and bottom by R-jwL. This is called "using the complex conjugate". It leaves a non complex number in the denominator and that's the beauty. The numerator will have j squared terms as well as j terms but then equate j squared to -1 because j is the square root of minus 1.