Thanks to a ScreenCastsOnline tutorial, I was reminded of Homebridge, a software system that allows interfacing 2000+ non-supported devices to HomeKit. I was pleased to see my iRobot Roomba 980 (and other models) was one of the devices supported.
The setup is a bit involved (tutorial linked above). There are several operating systems supported by Homebridge (Raspberry Pi, macOS, etc.). I used the Synology Docker install on my DS918+. (Go through the ‘Manual Install’, as they suggest, rather than trying to add the docker image yourself.)
You’ll also need the Roomba plugin for Homebridge, which can be installed from Homebridge’s plugins menu.
The Homebridge GUI has a QR code you can scan with your phone that will add it to HomeKit.
The end result is I now have my Roomba added to HomeKit, and can tell Siri to ‘start Preston’ and ‘stop Preston’. The plugin also provides three ‘sensors’ that can be used in automations, docked, running, and bin full.
No more waiting for iRobot, and things are a little more right in the world.