I started watching Touched By An Angel a few weeks ago and when I went to pick up where I left off yesterday, I couldn’t find it. Has it been removed from Roku? I surely hope not. I was really enjoying the series.
I can't speak to that show in particular, but in general programs come and go as streaming rights are acquired and expire.
You don't mention what channel it was on. Roku is only responsible for the Roku channel. Also, as noted, shows come and go, just like regular TV. They most commonly will be added/removed at the change of a month, or the 15th or so.