I have a Premiere + connected to a Sony TV. Then use a headphone to 2 RCA cable to connect Sony TV to Pioneer stereo. Buy a good quality cable; cheap ones (< $3) sound bad.
Sony TV:
* headphone./ audio out -- set on audio out;
* audio out -- set on variable. (can control volume of 35-year old Pioneer with $9 GE universal 4-device remote)
Pioneer sound quality is GREAT from Roku/Sony with no Snap-Crackle-Pop (CDs, mp3s (RMP), Blu-ray movies, DirecTV Now, Netflix). I bought Pioneer 35 years ago, and came with two 15"x31.5" speakers, phono, dual cassette, tuner, amp. I listen to some music every day from the Pioneer / Premiere + (YouTube, Pandora, RMP (447 mp3s on USB stick inserted in Belkin router [media server])), and all sound great. Before buying an expen$ive AVR, I think you should listen if a $7 cable from Amazon will fix your problem. Could try a $1 metal electrical box from Lowe's (4"x4"x2") to set Roku on for cooling, can't hurt anything. My Premiere + sets on an old not-in-use VCR with thin metal top.