If you want to super DIY it you could use a ESP8266 or ESP32 and the ST_Anything project: [RELEASE] ST_Anything v2.8 - Arduino/ESP8266/ESP32 to ST via ThingShield, Ethernet, or WiFi then use the vacuums own battery to run the board.
That would actually be pretty cool come to think of it…you could even “schedule” a old roomba that doesn’t have WiFi/BlueTooth by scheduling the point in SmartThings to turn on at a certain time.