the R installation in the "org.knime.ext.r3.bin.win32.x86_3.0.3.v201508240951" plugin should already have the Rserve package installed. You could try updating it.
While editing the preferences, there should be errors/warnings when editing the "Path to RHome". Try putting in an invalid path. If there are no errors, you should try updating the R integration plugin aswell.