I haven't tried installing Rosetta in Lion, but to me it sounds like at the moment Lion is simply asking itself the question "is this a PowerPC application?". If yes, just fail. Doesn't sound like its even loading the extensions, but someone should check in Console for errors. There may be nothing wrong with Rosetta kext's, because Rosetta already previously worked in Snow Leopard with the 64bit kernel.
Rosetta does not support kernel extensions (kext) and does not load kernel extensions.
I tried to bring native read/write ZFS support to Lion using the binaries from Snow Leopard beta 10a286. But, it fails because of the 64 bit kernel, and expects symbols in libkern which aren't present.
Only kernel extensions compiled with Xcode 4.1 or newer are compatible with Lion. Apple has a special version of Xcode 4 for their own development teams.