Found a hint, how to install Rosetta on Lion: Macwelt: Two tiny hints
"Recently discovered: On Lion, you can re-install Rosetta out of the Snow Leopard DVD. But since I've removed all of the PowerPC applications, I can't test this."
How to:
Insert Snow Leopard DVD
Open folder "Optional Installs"
Run "Optional Installs.mpkg"
In the installation application, just select "Rosetta", leave other options blank
Confirm upcoming dialogs.
Other sources:
Macworld: Nix Rosetta
MacGarden/Mac OS X (PPC) abandonware



