The G36 is a dual band AX router. Meaning it has 2.4ghz and 5ghz. 2.4ghz is a much slower network than 5ghz and its more sensitive to interference because there’s less channels available. I think what the user might have been trying to tell you is to change to the 5ghz band. Its significantly faster and has less interference. But sadly, it doesn’t broadcast as far or through as much materials. So users tend to select the 2.4ghz. Its also only in more expensive devices as the base model roku’s are only single band. What roku specifically do you have? If it has the 5ghz, connect to that. If it doesn’t, try changing what channel the router is broadcasting on in the 2.4ghz band as it might have interference from other routers/signals. 

It’s a Roku Premiere model 3920R, and it only has 2.4 GHz.  It’s using channel 1.  I’ll try switching to another channel.  Thanks.

Try 6 or 11 and see how they work.

Are you using it with a 4K setup? You can try setting the bandwidth down to 1080P and see if that’ll free up enough bandwidth to stream reliably

I just switched it to channel 11.  We’re not using 4K, just 1080p.