This is a quick run-down of how I installed Debian on my dedicated server (@ OVH - super cheap!), and managed to setup an encrypted rootfs with ssh during boot to unlock. This is both for the offchance that I'll have to do it again, and if anyone else is wanting to do the same thing. There are a few guides out there to get the unlocking over SSH, and a few for remote installation of Debian, but none that combine the two.
These instructions need an existing Debian install, although Ubuntu might work too.
Source for this part of the guide was here