There is a fairly simple answer with powershell.
Import-PfxCertificate -Password $secure_pw -CertStoreLocation Cert:\LocalMachine\Root -FilePath certs.pfx
The trick is making a "secure" password...
$plaintext_pw = 'PASSWORD';
$secure_pw = ConvertTo-SecureString $plaintext_pw -AsPlainText -Force;
Import-PfxCertificate -Password $secure_pw -CertStoreLocation Cert:\LocalMachine\Root -FilePath certs.pfx;