I have a Roku Ultra. When I turn off the my TV the Roku stays on for quite a long time. The problem with this is my internet has a monthly gigabyte max. So even though I'm no longer watching the TV the Roku stays on a long time using gigs. Long story short... Is there a way to turn off the Roku as soon as I'm done watching the TV?
If you want to just press the Power on the remote button then short answer is no. If you return to HOME screen before shutting down, then usage is really negligible, but still using "some" data, but nowhere near streaming data.
The easiest way is to just unplug the roku. Without power, it can't use any data. (Of course, the term easiest is relative depending on where your Ultra is located... you can disconnect at unit or at outlet/power strip w/switch etc.)
Other way is to configure router to deny internet access to Roku after a certain time of day (similar to parental controls) or manually deny access at router level roku's internet access either by laptop/phone app, etc. and then reenable when you go to watch it again.
I think if you remember to go to HOME screen before turning off the TV (which is what most people do I would assume) is the best way to drastically reduce data usage until it goes to sleep/hibernate mode. To completely turn off data usage, you will have to block internet access or cut power to the Ultra unit itself.
This is the way I used to do it when I was on a 250gb/mo plan. I remember checking my usage after everything I streamed to try and figure how much data I had used, how many more shows on average could I watch, etc.... plus using computers and everything else requiring data. Very happy when my Broadband offered me an unlimited plan for a couple dollars more when they upgraded their operations.
I just wanted to add that you can press home before and/or after turning off the TV, and you can just press home any time you want to make sure you're not consuming data. Roku doesn't know if the TV is on or off.