Seeing no characters on the Roku SceneGraph native keyboard in 1080p setting. ie. ui_resolutions=hd,fhd on 1080p UI supported Roku devices.
Dialog keyboard 720p:
https://c1.staticflickr.com/3/2868/3403 ... 0140_b.jpg
Dialog keyboard 1080p:
https://c1.staticflickr.com/3/2830/3403 ... 611f_b.jpg
Keyboard node 720p:
https://c1.staticflickr.com/3/2851/3403 ... c76b_b.jpg
Keyboard node 1080p:
https://c1.staticflickr.com/3/2866/3335 ... 9ccb_b.jpg
Seeing this on a Roku Ultra (US model) - 4640X
Software version: 7.5.1 - build 4111-29
To reproduce set your box to 1080p via Settings > Display type > 1080p HD TV
Side load the SceneGraphXMLTutorial.zip from the Roku dev blog.
Seeing the issue on the Dialog keyboard all types and the Keyboard node.