Lukasz,
Thanks again for assisting novice hobbyist (me).
It is not mandatory to use Remote Desktop to control ROSbot, but it is introduced in first tutorial as most basic use example. You can control ROSbot using Rviz launched on your local laptop or with Web UI. VG: I went to the husarion github website and will try Rviz. When using remmina on my laptop, the window is 1/4 the size. Is that normal?
The message you are seeing is warning regarding camera optical calibration.
The calibration file is required to fix optical distortions of the image. You can generate this file using camera_calibration1 tool.
Camera can work normally without the calibration file, you will be able to see camera image or perform object recognition. VG: thank again and provide link for calibration tool.