Universal applications run natively on Intel-based Macs, but on Mac OS X 10.6 or earlier there may be occasions - if they rely on plug-ins or drivers that have not yet been released in a Universal format for example - when you may need to run them non-natively in Rosetta.
With Application Wizard you can easily force Universal applications to run using Rosetta, either always or just once.
Open the Application Wizard pane in System Preferences and click Applications.
Click the Add (+) button at the bottom of the list, browse and select the application, and click Add.
Select the "Open using Rosetta" option. When launched from the Open menu the application will always run in Rosetta.
Select the application in the Open menu.
Press the Option key: if the application can run non-natively, its icon will switch to the Mac OS icon and Application Wizard will open it in Rosetta.
Note: Rosetta is no longer supported on Mac OS X 10.7. Universal applications may run slower when opened using Rosetta.