Roku Premiere 4620XB 4K UHD manuual - Roku Televison & Video

If you wish to get some details; visit the site linked here. Pull up older posts. Surf the site with patience.
Faults & possible causes to LCD & Plasma screen are given with illustrations. You can get an idea about the fault to an extent.

I am sure YouTube will give you the answer.

Try a google search providing the info /request manual I believe Roku has a pretty good customer service too

if using an hdtv antenna,it means that it has moved and cant pick up channel anymore,rescan for channels

That noise is caused by a failing component in the sounds amplifier circuit board.