Quantity   Component name
1 × Wemos D1 mini because they're small and cheap
1 × BOB-12009 bi-directrional logic level shifter
1 × R-785.0-0.5 Linear Regulator Replacement DC DC Converter 1 Output 5V 500mA 6.5V - 32V Input
1 × MD-70 Mini DIN 7 Male connector, Mini DIN 8 is fine as well
1 × Stripboard, headers and wires
1 × iRobot Roomba with their OI (open interface)
1 × Optional: Wemos D1 OLED Shielld