so don't take what I'm saying as gospel, but I'm basing my response on the two or three years of using my Roku 3 player. It has a USB port to load stuff, but so far the only thing I can run from it are media files; I have no idea how to load content that could potentially jailbreak it. And like I mentioned before, the automatic updating feature makes it that much harder to truly break the device.
Like I said before though, if someone knows better than me, they are free to correct me on my errors.
"Sean sparks like John Starks, nah, Sean ball like John Wall" - Rest In Power Forever Sean Price.