Not sure if this will help - but this is a quick recap of my notes on certs for JUNOS-ES -
1- Create a cert using whatever tool - I personally use Openssl.
2- Ftp the cert to your router
3- Install the cert onto the box -
set security certificates local jcert.pem new load-key-file jcert.pem (where jcert.pem is the name of the file containing the RSA key and cert data)
This command loads and activates the cert on the box.
4- Then set the https service on:
set web-management https local-certificate jcert.pem interface ge-0/0/3.0 .......