I do apologize that you are experiencing issues when casting to your Roku device. For more information as to why this is happening, please check out the link below. Hope this helps!
Sling Media Moderation Team
I am having a similar issue on an iPad Air, Roku 3, and Slingbox M2 (both wired Ethernet, both have latest firmware). I have steady video for about 4 to 7 minutes, then the video freezes on the Roku, even though the M2 streaming indicator is still on. I can switch back to iPad (it works), and switch to the Roku, and it works for several minutes, then freezes again. The streaming on the iPad does not freeze.
I am watching TV via slingbox at a remote location. I have no problems when I am watching on my ipad, but when I stream through my Roku 1 to the TV, after about 3 minutes the picture on TV freezes. If I disconnect and go back to my ipad it works fine again. Any ideas on how to stop the freezing on the TV?