ok i figured this out finally after 15 minutes lol it worked fine and paused unpaused then would not unpause, just said cannot find music playback device named roku so i looked online and noone here had a solution other than resume or continue which had the same result. then i realized that the alexa was actually stuck trying to playback a music list i had started and told her to cancel. so saying unpause roku resume roku or continue roku was trying to continue playing the music but the roku cannot do that so she was confused. so i just said alexa continue and sure enough the last song started right where i had told her to cancel music well it was an 80's song list of over 50 songs so what i did to get her out of the loop was played a short song and let it finish now she can resume roku just fine - hope this helps and they need to fix alexa to actually cancel and forget something when you tell her too not save it until something else replaces it.
After spending 43 minutes on the phone with echo support replicating the error over and over he finally submitted it to the development team to fix the cancel/stop music command to actually make it forget what it was playing so this will not happen anymore once they fix the problem. we even tried it with just 1 song and it still does it until the song plays all the way to the end then it will resume/continue/unpause roku just fine.
Is there an Alexa command that engages the Roku "find remote control" function? That alone would be a "killer app" level ability to convince some of our friends (who CONSTANTLY LOSE their Xfinity remotes) to join us in switching to Roku.