I may be wrong, however, I think that most of the rpms are designed to be removed once installed ... driven by the spec file.
Hopefully someone will correct me if I am mistaken.
If you wish to download the rpms via yum you can install yum-utils and
then use yumdownloader and direct the package(s) to a local directory. This will not install them it just downloads the packages.
There is more information located here:
has a much better solution here for you: