lol, yeah, "huh?" is right. A little more information, please. Do you mean you simply want to install one of the two 2.1 leaks from the stock 1.5? Or do you want to install one of the 2.1 leaks from your rooted 2.1?
You don't need to use adb to go from stock 1.5 to leaked 2.1, there are plenty of threads explaining how to do it in the main Eris forum. To go from rooted 2.1 to leaked 2.1 (don't know why anyone would want to do that) I'm not so sure, but I figure you would do the same thing as going from stock 1.5 to the leaked 2.1.