If bypassing your AVR magically make 4K content appear with the Roku Ultra, then there's something amiss with the AVR. The VSX-534 supports 4K, but you have to make sure all the internal video processing is turned off. It sounds like the VSX-534 has some sort of processing enabled that is only outputting 1080 to your display. I have two different Yamaha AVRs, both with an Ultra connected, and both passthrough 4K video without a problem.
Dan
Roku Community Streaming Expert
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