Unable to AirPlay on any Roku device from my iPad.

You did not provide enough information. What model of Roku player? If a Ultra or Roku TV, is it connected to your network via wired or wireless? How is your iPad connected to your home network? Is this a home network or are you using a public/shared network such as a hotel or other non-private network?

AirPlay is not a direct connection between the iOS device and the Roku. It communicates through the network, and there are security settings in public/shared networks that would block functions like AirPlay from working.