My Roku stick and my Mac are on the same wifi network, but the Roku stick does not appear in the options for screen mirroring on my Mac. I've tried restarting the system but that does not work.
On your Roku have you enabled Airplay via Settings > Apple AirPlauyand Homekit ?
Yes. Here's what I've tried:
I was able to screen mirror using a Windows laptop without issue, but cannot connect with my Macbook.