The Premiere 3920 is operating on your 2.4ghz band.
You may just be getting some interference or crowding/congestion on this band.
Try going into your router settings (or an accompanying app if available) and adjusting the "wifi channel" that the 2.4 ghz band is using. Generally, channels 1, 6, or 11 are recommended but you may find in your setup and environment that you have to use another. (compatible channels are 1-11 for Roku).
Most routers are setup to use "auto" channel selection by default, meaning they will change automatically according to certain conditions. Some routers handle this better than others, so a manual channel setting may be needed to fine tune and optimize the network instead.
Feel free to post back with router model number and ISP (internet service provider) if needing more help.
