In order to utilize the two cores in a duo core machine, a program needs to be compiled with parallel library such MPI. It is obvious that you did not run a parallel version of rosetta. At first, you need to have MPI library correctly installed to system. Then, you should recompile rosetta to link the mpirun library (use mpilam option).
> may i know the command to run rosetta.gcc in multiple processor (intel Core 2 duo)