If you haven't done so yet, see if there are any firmware or software updates for the box. I can't remember which Roku does, but I probably never did any on that one, so that might add more channels for you.
I've never found many great free channels. There were some classic movies, some classic cartoons, a German news channel, and a couple of decent outdoor / shooting channels. Otherwise, it could be worth an investment in either Netflix, Amazon Prime, or Hulu, depending on which service has more of what you like.
I don't think Hulu does free anymore, and the first tier of pay still does commercials. I used it for a while and it drove me crazy. A few months ago, they started a second tier that's commercial free at $11/mo. They do have a free trial period, so you could always try that to see if it floats your boat.
If I could have only one service though, it would probably be either Netflix (more content bang for the buck) or Amazon Prime (decent content bang for the buck, but you get a ton more of other neato stuff with the Prime membership (worthwhile if you use said neato stuff)).