I suspect the Impecca TV (or some intermediate device if not connecting directly to the TV) is not correctly reporting the TV's capabilities when the Roku and TV do their "HDMI handshake" to find mutually-acceptable protocols to use.
Suggest you set the problem Roku(s) up on a TV where they DO work. Set Settings > Display type to a basic 720p resolution, not an "auto detect" setting. Now move to the Impecca set and see if it will display.
If it does, and if the set has a greater than 720p resolution, go back into Settings > Display type and don't rely on "auto detect" but experiment with other specific settings until you find the highest one that works.