If I understand your dilemma correctly, you are essentially trying to view your PS Vue content through the Roku Premiere+ using your Slingbox. This may not be possible as you would need to find a way to control and view the Roku.
If your Roku model is HDCP compliant, you may not get any video or sound through an HDMI connection. Secondly, you would need to make sure your Roku uses IR in order for the Slingbox to control your device remotely. The links below will provide more information on this.
- Slingbox.com - Using an HDMI video source with the Slingbox 500
- Slingbox.com - Advanced IR emitter or onscreen remote control troubleshooting
Sling Media Moderation Team