Sorry, still confused and apologies if I'm thread-jacking -
If I see an episode/show/content marked as "Hulu Plus" on the site, can I expect it to be available on my Roku?
It's really not that complicated. Look to see if it has a plus icon. Now hover the mouse over the shows icon and it will tell you if you can watch it on mobile, web, and TV or it will have a "sorry, this is only available online." For example look for the show Castle. Hold the mouse over the picture and see what the pop up says. Now look for Barney Miller. No Plus Icon and no message saying it can be viewed on the TV. No message equals no it can't.
You can also filter the search for TV available episodes.
There are promos to give you free time so just sign up for it and try it out. It has a million viewers (or almost, I can't recall how it's worded) and if you fine one show you like then consider it a bargain rental. I've had it and I like it so much I paid a year in advance for it. I literally haven't watched broadcast TV in months because of Hulu.