Is there a replacement for Rosetta in Lion?
I know it sucks, but really you might just need to drop the PPC stuff (Apple isn't going to support it at all in the future) or look into trying to get the source code and recompiling it yourself.
At this point, the open source PPC Mac emulator Sheepshaver may be your best bet.
Install Snow Leopard (and Rosetta) in Parallels 7 in Lion. Installation guide here:
http://forums.macrumors.com/showthread.php?t=1365439