Even though the iRobot line of smart vacuums doesn't support Apple HomeKit, there is a way to control your iRobot Roomba with Siri. It's not as simple as downloading an app and pushing a button, but it's not overly complex either.
If you're in a tinkering mood, then you're going to have a blast, and in about 5 minutes, you should be able to command your Roomba using Siri on your iPhone, iPad, Mac or even HomePod.