@cushant Thanks for the question! There isn't directly a 'last channel' button, however there are a couple ways to launch channels with one click.
Using our voice search features, you can launch many channels by pressing the voice search button on your remote, or tapping the microphone icon on the Remote tab of the Roku mobile app while connected to your device, and saying 'Launch [channel name]'.
You can also go to the 'Channels' tab of the Roku mobile app, locate the channel you want to launch, and select it to load the channel.
Thanks for sharing the question and interest in that type of feature. Feel free to visit the 'Suggest a feature' section of the Community to add your thought!