"not compatible with this signal" ultra device

That warning is probably generated by the TV, not the Roku. saying the video format being sent by the Roku is not one supported by the set.  Perhaps something has caused your Roku's Display setting to get changed.  Without being able to see what you're doing on screen, it makes it tough to change any settings.

If all else fails, you can try to adjust the Settings > Display type setting when you can't see the screen. After booting up the Roku and getting past the bouncing letters startup display:

A• Press the remote Home button 2 times (Makes sure you're on the home screen at correct position with no screen saver running)

B• Up (Go to Settings)

C• OK or Right (Go into Settings options)

D• Down 3 times (Highlight Display type. It passes through Theme on the way and this may take a few seconds before moving on) so wait 30 seconds or so before continuing.

D• OK (Chooses Display Type option)

F• Up (Moves off current Display Type setting to next one up)

G• OK (Selects this Display Type setting)

At this point, the Roku will try to use the selected Display Type setting. The TV may take a few seconds to adjust to this new setting.

If you see a picture, click the "Yes, looks good" button to lock in this setting.

If you don't see anything, wait about 15 seconds, then hit OK to click the unseen default "No, there's a problem" button to return you to the menu.

H• If you have not found a resolution setting that works, repeat steps F and G to try the next Display option. Repeat until you find one that works.