My Roku is set up to cable by coaxial from wall to TV. I can watch shows on cable and there is not static…until…with a small add pops up during the show or a commercial comes on. There is never any static any other time. Just during commercials and when words come up on the screen. For example, watching espn and other scores states to scroll across the screen. Or just having the score on the screen makes it staticky.
It's possible that the issue you are experiencing is related to the commercials through the cable if it is only occurring during commercials. Does this issue happen on other TVs that are connected to the coaxial as well?
Please keep us posted and we will be able to assist you further.