Snes-O-rama has a fuckload of dreamcast roms along w/ burning instructions.
Best burning program you wanna use is Alcohol 120%...and burn with the RAW DAO(Disc-at-once) setting. I will warn you though....playing with burned discs eventually wears your lens laser engine down. I'd buy some extras just in case....I still have to buy another for my own. Unfortunately the 360 keeps distracting me.
I will tell you this though. There are many dreamcast isos with EMULATORS and ROMS on them. Like I have a disc w/ NES emulator that has all roms, nes, and genesis. Great shit.