The side-stolicks are connected with the SEC computers, why? Is it for the roll order?

Yes,  SEC (Spoiler & Elevator Control)  Spoilers assist with roll control.   As explained to you previously - Side stick sends signals to the ELACS which then send the signal to the SECS

Thanks so why do we use spoilers in cross winds?

The pilote will basically turn with the stick but the ELAC computer sometimes sends it to the SEC computers, is it faster or better? And I imagine only one wing's spoilers will come...

 

Thanks FLEX