It's been asked and answered. At this time Roku has no plans to offer AirPlay on any device that doesn't already have it. They have to license it from Apple, and that likely isn't cheap.
Dan
Roku Stick (3600), Ultra (4640), Ultra (4670), Ultra (4800), Premiere (3920), Insignia 720p Roku TV, Sharp 4K Roku TV, Nvidia Shield, Windows 10 Pro x64 running Serviio and Plex on a wired Gigabit network.