Actually, before you try that, try rpmbuild --rebuild NVIDIA_kernel-1.0-4191.src.rpm instead (i.e. replace rpm with rpmbuild in the command). RedHat recently moved all the rpm-devel stuff into a separate executable, rpmbuild.
If that still doesn't work, then boot to your RH installation CD, select "upgrade" rather than "install", and select the appropriate packages inside the installer. Alternatively, you could search around on the CDs for the rpm-devel RPM and install it manually, but there is the possibility of you running into dependency problems that way. When you use the CD's native package installer, the dependencies get installed for you.