For the application, which one do you recommend, by spray or by roller?

There is a difference in workability.
The application speed by spray is faster with seamless finish, but the paint splatters around a lot. If you do not properly protect the surroundings when painting, it will cause trouble and inconvenience to neighboring residents.
On the other hand, roller application requires more time for application, but it is less likely to scatter. It is suitable for high places and areas where houses are densely built.