You can attach the Laser Range Finder from the Pioneer 3DX sample. What you need to do is edit the saved simulation engine state and copy/paste the LRF into your saved sim state. Then copy/paste the corresponding section from the manifest for the Pioneer
3DX into your manifest. That's a brief description.
Alternatively, look at the code for the Pioneer 3DX sample and add the LRF to the Corobot programmatically.