It should be. But after installing OS X 10.6 on my Mini 10v, I was able to install Office 2008 without it asking me to install Rosetta. Puzzling: I've always thought Rosetta was an integral part of recent versions of OS X and installed automatically.
Here is what it says at the Apple web site:
"New applications bearing the Universal symbol will run natively on both Intel- and PowerPC-based Mac computers. What about the applications you already own? Enter Rosetta. You’ll never see it, you’ll never configure it, you’ll never have to think about it. It’s built into Mac OS X to ensure that most of your existing applications live a long and fruitful life.
Protect your investment
Here are all the instructions you’ll need: double-click the application icon. Behind the scenes, Rosetta dynamically translates most of your PowerPC-based applications to work with your Intel-based Mac. There’s no emulation. No second-class status. It looks and feels just like it did before. On a Mac, you’d expect nothing less."
so I'm puzzled that you would have to install it.