I have no problem with flossing my teeth in any room. I often do it in bed while listening to podcasts. As long as you are being somewhat mindful about what teeth you are up to and getting the job done, I can't see any issues.
If watching tv while you do it helps, do it! If it’s your house, it’s up to you. Some roommates might get weirded out (because plaque might get sling-shot around), but if that’s not an issue for you, do you!