If she goes Banner and Zzrot and you can't kill her with your jungler, that's when she wins. Your jungler is supposed to camp your lane 24/7 there, and once she's sufficiently far behind, THEN you roam. If you roam with her still being in the lane and your jungler not paying any kind of attention to it, you'll at BEST get a few kills on bot/top for the price of both your towers on mid. That's not worth it, unless you get a drag every time it's up on top of getting all those kills on bot. That's why it's not worth it, and your jungler should've done a better job at camping your lane for the first 15 minutes.