You would need a dinothawr core I think, this user looks like he has compiled one:
http://libretro.com/forums/showthread.php?t=725

Here are the steps I followed:

Get the dinothawr game files on the Pi
Put game files (dinothawr-data.zip unzipped) here:
/home/pi/RetroPie/roms/ports/dinothawr

Copy the dinothawr core across
Create /opt/retropie/libretrocores/lr-dinothawr
put dinothawr_libretro.so in it (attached below)

Create config setup
Create /opt/retropie/configs/dinothawr
create retroarch.cfg for it
Put this in it

#include "/opt/retropie/configs/all/retroarch.cfg"
# All settings made here will override the global settings for the current emulator core
input_remapping_directory = /opt/retropie/configs/dinothawr/

Create ES Menu item
Create Dinothawr.sh in
/home/pi/RetroPie/roms/ports/

Put this in it

#!/bin/bash
/opt/retropie/supplementary/runcommand/runcommand.sh 0 "/opt/retropie/emulators/retroarch/bin/retroarch -L /opt/retropie/libretrocores/lr-dinothawr/dinothawr_libretro.so --config /opt/retropie/configs/dinothawr/retroarch.cfg /home/pi/RetroPie/roms/ports/dinothawr/dinothawr.game" "dinothawr"

You can get the game files here:
http://themaister.net/dinothawr/dinothawr-data.zip

The libretro core is attached.