Roku Express. Worked fine last night. Today, black screen. I've tried all the troubleshooting, unplug, wait, plus back in, etc. I get the jumping "Roku" start screen then just goes black. Extremely annoying!
This may indicate the Roku is trying to send in a resolution the tv does not support.
I'd suggest trying the Roku on a different TV if one is available, especially if it has a working Roku. If it comes up okay there, go into Settings > Display type and change the Roku to the actual resolution of the problem set instead of the "auto" setting. When you get to the countdown screen click on the "yes" option to lock in the setting. Now move the Roku back to the first set and see if it works.
Let us know how you make out.