I just got a TCL roku tv and setup slingplayer. First thing is I didn't realize you needed to cast to roku I thought it would work more like Netflix but anyway I cannot cast to roku.
I have latest android app and I believe latest roku slingplayer app. I'm on the same network as roku. Also made slingplayer first in app list. No option for casting to roku. Doesn't give option for Chromecast either. One odd thing to note is that the first time I add roku to slingplayer app it spins and spins for a long time. After exiting and readding the roku it finds it right away.
Also note that I can view the channels on my android. I just cannot cast to roku or Chromecast.