Rokus don't seem to ever "turn off". as long as you switch the TV input to the Roku and it's plugged in, it's on the TV. At least that's how our 2 work.
The amount of apps available is enormous. Some free, some added cost. We don't have one that we pay for. One thing we use it for is to watch Syracuse University basketball. During the regular season they are usually on ACCN Atlantic coast conference network that is not televised down here. With the ESPN app we can log into our Verison FiOS account up north and watch almost every game.