Only getting desktop when casting to Roku

I'm trying to mirror my laptop on my Roku, which apparently is a thing I learned today. I've connected in W10 settings and allowed the Roku to mirror my HP Spectre. I see my desktop on my television screen, along with the taskbar at the bottom. But nothing else seems to be getting sent to the Roku - browser, apps, etc. When I click on a different icon on the taskbar, I even see that icon get highlighted, but nothing else appears on the television. This might be a discussion for a Roku forum. I'll try there as well. For what it's worth, my Windows phone works flawlessly when mirrored through the Roku.