Owners of smart TVs and streaming sticks running Roku OS are already subject to video advertisements on the home screen. Now, Roku is testing what it might look like if it took things a step further and forced people to watch a video ad play before getting to the Roku OS home screen. Reports of Roku customers seeing video ads automatically play before they could view the OS’ home screen started appearing online this week. A Reddit user, for example, posted yesterday: “I just turned on my Roku an...