I don't know what equipment you have but if you have a laptop running windows 8..Hit the windows key and c. You'll get a list on the right. If you click devices and then project you can cast to roku . I'm not sure if windows 10 is the same.
Its pointless what I said but trying to help.
It works for me in a pinch.
God bless man.
I'll try win 10 tomorrow if i don't forget.