I have a couple of Rokus but not the Express (and I want one for travel). Roku's feature chart shows Cast support for the Express: https://image.roku.com/ww/docs/compare-chart-products-en.pdf
So I'm curious if you see the Cast icon on the upper left corner of the app. If you don't see the Cast icon, you are not able to cast. When you tap the cast icon, the app will ask you where to switch (for example there will be check boxes to select Android or Roku xxx).
You can be connected, but unable to cast from the app to the Roku. Let me know if you got this to work before I buy an Express.
Thanks for your interest and encouragement. This led to a diagnosis and, with the aid of a Slingbox technician, I was able to get it to work. Even though Slingbox doesn't specifically list the Roku Express on the Slingbox's Roku-compatibiltiy website, it does work fine (as you suggest it should).
The problem turned out to be that I was using composite input to my Slingbox M1 (it had nothing to do with casting from Slingplayer to the Roku Express). For some reason, the Slingbox M1 would not sling composite input over the Internet, even tho it passed that input to the local output.
This took some time for me to diagnose:
1. When using component input/output everything worked fine and I was able to cast to the Roku Express.
2. Serendipitously, when I tried slinging with the composite input to a Windows10 PC, while it didn't work, it showed an option to select the slingbox's input. When I couldn't find a way to change the input from component to composite, I called a Slingbox technician.
3. I explained the situation to the technician . She logged into the slingbox (as admin?) and changed the input to composite. This solved the problem.
I'd hate to think that I have to call Slingbox everytime that I want to change my slingbox input (or output) from component to composite (or vice versa). The slingbox should be able to detect and automatically set up its input/output!
1. I only used one input (composite or component) at a time to my Slingbox M1. This is why the M1 should have automatically selected the proper input.
2. The title of this topic should be changed to Slingbox M1 requires input control. (I don't know how to edit the title.)
3. I consider the problem solved and the question ANSWERED. (I don't know how to set this.)
4. One more shout out to Robert for his Reply, which kept me optimistic that there was light at the end of the tunnel.
I have a slingbox M1 and bought a roku EXPRESS to stream video to another TV in my house. I reloaded the slingplayer app on both my android phone and on my roku and ensured that phone & roku were on the same home network. When this didn't work, I manually loaded the roku's IP address into the phone's slingplayer. Behold, the app said that it was connected to the roku, but I still couldn't stream to the TV. Then, I checked and was disappointed to see that the EXPRESS was not on the list of supported roku's!
Please create/configure/install (or whatever) in the slingplayer support for the roku EXPRESS! I bought the EXPRESS because of its performance, size, connections, and cost. The low cost, itself, could motivate many others to purchase a slingbox to eliminate the monthly expense of a cable box. Thanks.