I have a Roku 2 connected to my network via Ethernet. When it is just the Roku everything is fine. Whenever I am playing games on my computer and someone starts streaming, the connection to the computer drops to almost nothing. I've tried both wired and wireless. Same problem. Speedtest averages ~25Mbps up and ~3Mbps down. I also have a Chromecast which doesn't seem to cause any trouble. Any thoughts or suggestions?
Are you sure you have the speedtest figures the right way round? Most internet service has much less up than down
If you are truly only getting 3mbs down, well that's your problem. HD needs between 2-4mbs, and sounds like your router is giving priority to Roku, not computer, so if speed test truly says 3mbs, then there is nothing left.