If your Roku device is separate from the TV, you might be able to put the Roku as an input (HDMI) to the DVR and output of the DVR to the TV. Bear in mind, though, that the DVR is not going to be able to record something different than you are watching, because the output of the Roku is _only_ what you have selected to watch. So, I don't think it's really going to be that effective for you.
