Where can I find Python code for the Romi encoder
The Romi encoders output standard quadrature encoder signals, so they could probably be used with any quadrature encoder code. With a quick search, you should find lots of resources for reading quadrature encoders directly with a Raspberry Pi and python code.
If you are using our Romi 32U4 Control Board with your RPi, you could use our Raspberry Pi slave library for Arduino which off-loads low level tasks like motor control and reading the encoders to the 32U4 controller. The library provides a basic python example of how the RPi communicates over I2C with the 32U4 controller.