If you had a surround sound system, you could run all inputs into that and 1 HDMI out into 1 HDMI of your TV.
But it not, you need an HDMI switch box.
Or use Black Magic and create a new port on our TV.
I bought what I thought was a three way HDMI plug that would solve the problem. I notice it has three separate buttons on it for setting the right channel. My thought was, I could plug one of the HDMI cables and the ROKU cable into this, and plug both into an HDMI plug. Unfortunately, if I detach the cable from the cable box I get, obviously, nothing, and if I detach the cable from the DVD player I can receive ROKU on the channel that used to play DVD, but DVD is gone. What about: Using the 3 way, plugging all three devices into it, and using just one HDMI port?