It is highly unlikely that a dealer could control the ball in roulette. In a properly run casino, the roulette wheel and ball are carefully designed and manufactured to ensure that the outcome of each spin is random and unbiased. The dealer's role is primarily to spin the wheel and release the ball, but they have no control over where the ball lands.
In addition, casinos have strict regulations and monitoring procedures in place to prevent any form of cheating, including dealer manipulation of the ball. The wheel and the ball are also subject to frequent inspection and maintenance to ensure that they are functioning properly and in a random manner.
Overall, while there have been instances of cheating in the past, modern casinos use advanced technology and security measures to prevent such occurrences and ensure fair gameplay for all players.