First, we have no idea what model Roku you just purchased. There was a "Roku HD" player, but that was 11 years ago and that player is no longer supported. You should see the model number printed on the case somewhere, or it should be on the box the Roku came in.
The next question is what is the make/model of TV you are connecting the Roku to. Some early TVs with HDMI jacks didn't actually support 1080p or 720p signals, which are the only two resolutions available from today's Roku players (other than the 4K models which also support 2160p).
Dan
Roku Community Streaming Expert
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