However, I can tell from your download/upload rates that your router/gateway is WAN-speed limited to 100Mbps (since your download is slightly less than your upload).
And when I look up the specs of the TP-Link TL-WR941ND, it only has a 100Mbps WAN port (and LAN ports), so your router/gateway is the limiting factor and its WAN port is being saturated with multiple simultaneous devices/connections, and its processor is unable to keep up with the load, so dropped packets/connections/reboots are the result.
It also only supports Wireless-N (WiFi 4 - 2009), which is a 12 year old WiFi standard - the current standard is Wireless-AX (WiFi 6 - 2019/2021). Roku devices with 5Ghz support Wireless-AC (WiFi 5 - Wave1=2013, Wave2=2016)
You need to replace your router/gateway with one that has: 1Gbps WAN/LAN ports, WiFi 6/6e