So sad that I just bought a ROKU express and now find that this 1/4 scree problem has bee around for at least a whole year! I was so excited setting it up and entering all my details... eager to try it out then BAM! Only 1/4 screen display. About the size of my iPad. Soooo disappointing. This is a ROKU problem... with no apparent fix. That’s a shame.
I was having the tiny screen issue as well... Always while streaming NBC. Exiting and restarting fixed it but then had to watch 5 commercials before the show continued... Grrrr. I followed the instructions given here and checked for system updates in "Settings" and sure enough, NBC was the only one with an update waiting. So far, so good, thanks RokuTannerD!!