I have reason to not doubt them though.
My apologies everyone. The info I posted earlier has proven to be false(which, really, there's no surprise. I mean a 1gb DS game? Really Cello?)
The ROM size is 256MB in size, as proven by:
Mods, don't worry, it's not a link to the ROM. Koby_Akid has managed to dump the ROM but has no plan to distribute it, merely come up with cheats for B/W.
That's all. :D