Is there any way to run a PowerPC video game (Call Of Duty United Offensive) on Mavericks?
No,there really is not an easy way to run PPC apps on Mac anymore. Your OS X Rosetta disk will definitely  fail to install on Mavericks. Apple stripped support for Rosetta following the release of OS X Lion (10.7) and have never put it back. 

However, you still have a few (harder) options.


Install Snow Leopard in a virtual machine. Here's a guide.
Pull out your old PowerPC Mac, if you still have it.
Install Snow Leopard in a external hard drive or internal partition and use Rosetta.


When Apple first published Rosetta, they said it was best for low computational apps like Word. In addition, Apple stated that games and high computational apps like CAD software or video editors/compositors would have issues running through Rosetta. COD will probably not run well through Rosetta.

If all else fails, people still sell their old PPC's on eBay.