This has got to be the cheapest mini-sized Windows box yet. Only drawback is that it does not have built-in WiFi, and that it still has a fan, unlike the latest ZOTAC series.
Hard to go past at this price though if you're in the market for a cheap Windows box. The 2957U is Haswell-architecture too.
Yup the Roku has a USB port.
If everything is on your laptop and you're simply looking for the easiest way to watch the content on your TV, what about simply using a HDMI cable or something like ChromeCast? No need to set up a Plex server or a whole other PC. Or do you want something that won't need your laptop to be running?