If you can get temporary access to the internet, you can set up the free PLEX server on you computer.
https://plex.tv/
More cheaply than buying a Roku, Chromecast will work with PLEX and stream any video that will play in the computer's Chrome browser to your TV. It may also require temporary access to the Internet for setup.
http://www.google.com/intl/en-US/chrome/devices/chromecast/
If you TV will work with DNLA, another option is to set up DNLA on the computer. But you will be limited to the file types and sizes the TV can decode. In my experience, this works great for music and images and not all that well for video. That's why I went with Plex.