There is another option...
Get an external HDMI switch that has a toslink/digital coax output that can still do 5.1(many HDMI switches with a secondary audio output still dumb the audio down to 2.0)...then...
Roku and STB to the switch. Switch HDMI to the TV(again assuming the TV has 2). Switch toslink/digital coax to the HTiB.
Now if the TV only has one HDMI...you'd run the HTiB to the switch as well...and the switch back into the HTiB...
Welcome to the pratfalls and end arounds required with HTiB.
Get an external HDMI switch that has a toslink/digital coax output that can still do 5.1(many HDMI switches with a secondary audio output still dumb the audio down to 2.0)...then...
Roku and STB to the switch. Switch HDMI to the TV(again assuming the TV has 2). Switch toslink/digital coax to the HTiB.
Now if the TV only has one HDMI...you'd run the HTiB to the switch as well...and the switch back into the HTiB...
Welcome to the pratfalls and end arounds required with HTiB.