The endless stream of Big Pharma commercials has gone past the point of ridiculousness and we've entered insanity territory. You should fix that and soon.
Content has to be paid for somehow. Roku is an advertising medium. If you don't wish to see ads, then subscribe to the many channels that offer content without commercials.
As author Robert Heinlein said, "There ain't no such thing as a free lunch!"
You need to mention where you are seeing the ads. Roku only has control over the home screen and the Roku channel programming. They have little to no control over ads in other channels, including those you can access through the Roku channel.
Move to the UK. Not really a problem here (a few adverts for OTC drugs, no prescription).