I just got a Roku Ultra Friday early afternoon and fired it up, put a few channels on it, but have watched no more than 2 hours/day. When I'm not watching I go to Home, and then switch from the Roku's HDMI input to the TV and power off. The Roku Ultra does stay plugged in, though.
I checked my data usage today and for Friday it was 9.3 GB, Saturday 12.4GB and Sunday 10.7 GB. My data usage before Roku Ultra averages less than 5 GB/day and has never been this high (I can and do check daily usage ever since getting 3 Amazon Fire TV Sticks several months ago, and even with them plugged in all the time I use < 5 GB/day).
Clearly this more than doubling of data usage is linked to the Roku. What can I do to troubleshoot this and stop it?