Then install them using:
wusa <RSAT Installer Filename>.msu /quiet
You can then enable the Powershell AD cmdlets (or indeed any other RSAT components) from the command line using dism.exe thus (careful, the featurenames are case-sensitive):
dism /online /enable-feature /featurename:RemoteServerAdministrationTools /featurename:RemoteServerAdministrationTools-Roles /featurename:RemoteServerAdministrationTools-Roles-AD /featurename:RemoteServerAdministrationTools-Roles-AD-Powershell
For some reason it won’t install “dependent” parent components unless you explicitly tell it to install them, which is a pain but workaroundable.