It means look what’s called in the script and go check if the file is actually there.
When I look at my service file (for Roon Server, not Roon Bridge but I don’t think that matters much) for example, there is no /bin/bash for exec. I don’t know why you added that (you may still have to deal with SELinux and if properly done the service file should work without modification). Furthermore:
This looks like a typo to me. Wasn’t there supposed to be a space in there somewhere? As I don’t run Roon Bridge on my CentOS system, I can’t check the commands inside its start.sh for you. Please check yourself if the commands called inside point at the right places.