For both to suddenly lose connection, it's highly unlikely the problem lies with the Rokus themselves. What has most likely happened is your ISP has made a change to your router settings (they can do that with ISP provided equipment) that has impacted the Roku connections. Without knowing exactly which model Premiere you have (there's 2 versions of the Premiere+ and three versions of Premiere) I can only make a guess. But the likely issue is that your router has changed its WiFi channel number on the 5GHz radio to one of the DFS channels, which are not supported by your Roku 3 or the Premiere+ that has a dual band radio. Your computers likely support using a DFS channel, so no problem. Assuming the 2.4 GHz radio is enabled (some ISPs have been turning that radio off) the router might be using channels 12, 13 or 14, which no Roku supports. On 2.4GHz Rokus only work on channels 1-11. Only the latest versions of Roku players support DFS channels on 5GHz.
By default most routers will automatically use a channel that it feels has less interference, and that channel can change without your knowledge. If the new channel is supported by your WiFi device (such as your computers) it's seamless and you never know it happened. But for devices (like the Roku) that doesn't support every channel, you have a sudden loss of connection, and your Roku cannot even see the WiFi to connect.
Dan
Roku Community Streaming Expert
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