Javier,
The arduino.cc Uno Rev 3 is the one I was thinking of.
The arduino.cc Relay shield you linked will provide the easiest installation. It uses fixed assigned pins on the Arduino Uno. Those pin numbers are used by default in the rolloff.ino.standard.
For a one button controller use relay 1, for two button use relay 1 for open and relay 2 to close. The normally open relay connector is used along with the common.

On the input side the default pins will be A0 to indicate fully opened and A1 for fully closed. You can see these definitions at the start of rolloff.ino.standard. The uno's builtin pullup resistors are used so switch opened will be pulled up to the positive value. When the switches are closed your connection will be from the pin via the switch to one of the ground pins.
Given these hardware selections you will not need to make any changes to the ino code. Rename the sketch to rolloff.ino and place it in a sub directory named rolloff. Then use the Arduino IDE to load the sketch onto the board. Then you get the USB connection from the driver working.
Could bench test when you get the controller or get the controller working safely and reliably on the roof and then introduce the uno connection.

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