Hellow @marina97 ,
I am not the specialist, but I think I can help you ( @edouard-renard is the Niryo One specialist).
The raspberry is a hardware the runs with Raspbian Linux Operational System .
ROS – Robot Operarional System runs inside the rpi OS to control the niryo one robot arm:
This is how to install – http://wiki.ros.org/kinetic/Installation/Ubuntu
The Robot Operating System (ROS) is a flexible framework for writing robot software. It is a collection of tools, libraries, and conventions that aim to simplify the task of creating complex and robust robot behavior across a wide variety of robotic platforms.
The Niryo One image has already everything you need concerning the software : https://niryo.com/download/
You also need to print the parts: according to your version : https://github.com/NiryoRobotics/niryo_one
Here you can learn ROS , Python and C++ : https://www.udemy.com/
Here in Brazil , I boght the nema17 for the 1 to 4 stepper motors at https://www.mercadolivre.com.br/.
The dynamixel for axis 5_1, 5_2, 6 and 12 (gripper 2) I boght from the USA http://www.robotis.us/ .
I hope this has helped you .
by Carlos Oliveira