This saves the precious bandwidth for the game one is playing. Remember when the voice activation enabled, it transmits all sounds not just voice. This includes sound from the speakers. The only way to get around this is to use a headset which is also supported by Roger Wilco. Any button can be configured to work as a transmit button.
Some controllers even have the capability to have a button configured as the transmit button.
There are some games that require specific changes in the settings of the software so that Roger Wilco will work. The compatibility page addresses most of the popular games on the market. Roger Wilco is best used with a sound card that has full duplex. Half duplex cards will work but you will only be able to receive. That is not very fun.