The Basics:
Applying patches to rockbox means:
- installing a compiler environment (on windows you can use cygwin or VMWare, I would recommend VMWare)
- downloading the source coude and the patch
- applying the patch (which is a text file containing the changes to the source) with a patch program
- compiling the patched source (I would recommend to compile a Simulator build first to make sure the build is working)
You can find guides to every step in the Wiki, SimpleGuideToCompiling is a good start, WorkingWithPatches and UsingCVS and VMWareDevelopmentPlatform are a good read, too.
And no, there is no easier way.