You could try XNA game studio. From the looks of it that's what 5th Gear uses. Students can get it for free off of
Dreamspark. If you have issues registering just email Microsoft and they should send you a code to complete your registration. Also, you can try
Unity. Team 1986 used it to do their field simulation this year.
Both of them do work with Autodesk (.fbx) files so you can use any CAD design of your robot directly. I hope this helps!