This question has been asked all over the Net during the last decade or so. I just encountered this topic again today and thought I would address it here.
No, there is not a way to play Genesis/Megadrive ROMs on the Sega CD. The system does not have a way to nativly play them. It also does not have the horsepower to emulate itself.
The closest thing to this was an attempt to convert Neo-Geo ROMs to Neo-Geo CD format. The project produced a couple successful conversions, but it seems to have been killed off.