The pins you are referring to are not connected to the microcontroller on the Romi 32U4 Control Board. The Raspberry Pi interface on the Romi 32U4 Control Board is intended for I2C communication (instead of UART). You can read more about this in the “Raspberry Pi interface and level shifters” section of the Romi 32U4 Control Board user’s guide.
If you want to use TTL serial communication from the UART pins (0 and 1), you can connect them to the appropriate Raspberry Pi GPIO pins, which are brought out in the corner of the board. However, please note that you should make use of the dedicated level shifters on the Romi 32U4 Control Board to reduce the 5V signal from the TX pin (pin 1) to 3.3V before connecting it to the Raspberry Pi. You can find an explanation of the dedicated level shifter pins in the same “Raspberry Pi interface and level shifters” section linked above.
Also, since you only mentioned TX and RX connections, you should make sure you also have a common ground connection with your TTL-to-USB adapter.