My old TV does not have HDMI-ARC/CEC or Digital Audio. Is there some kind of adapter you can buy in order to set up the Roku Streambar?
You don't need arc or optical output to finish setting up the streambar. Yes it will put screen saying you don't have hdmi-arc, click your tv doesn't have one, then when it ask if you optical and separate hdmi plugged in click yes and go on activating the streambar.
You need an arc or optical output if you want to hear other components connected to your tv through the streambar, but you don't need them if your only source is the roku built-in to the streambar. If you can live that, it should fine.
I have streambar connected to computer monitor, no arc or optical. It acts as the computer speakers, and I can stream apps and leave audio with streambar and video with monitor.