I'm not so sure I agree with that. I do agree that if the players had an HD view of the table then magnetic movements may be visible. But depending on how elaborate the magnet system is it could be made to be really hard to detect. And since most displays of the live feed aren't really very HD the magnets wouldn't even have to be all that elaborate. If there were a trusted 3rd party inspection service that would make the tables more trustworthy. I don't trust roulette any ways. There are other games to play with better odds to win.
The thing with magnetic movements is that they usually will have to employ some strong force on the ball, for the reason that if they wish to stop a ball at a place other than near a group of numbers, then they will have to slow down the ball, and applying a large magnetic field on it. Doing so will clearly bend the ball inwards, as it usually spins away from the wheel initially, and that unexpected movement will become fairly well visible to the eye .
Also , this actually would mean sensing what is the approximate position for the ball to stop at, and all that is pretty hard to implement. However, I am not sure of it myself, but just don't expect casinos to be using a magnetic system.