I've used a TI emulator before. Most of their ROM's are available from the Texas Instruments website (for purposes of restoring your device). Generally speaking, you should own the actual device if you're going to use an emulator/ROM. Will see if I can dig up some links.
Edit:
I think this was the
emulator I used. You can also find instructions on that site for downloading the ROM from a TI calculator that you own.