To make everything work you need a Synology box of some sort, a Roku box or the Now/Sky variant, the DS Video channel (download from Roku) and the Video Station application installed on the Synology. Load the Synology with your videos (you can rip DVDs using tools such as DVDFab and Handbrake) and let it think about things for a little while. The Video Station application will index your videos by searching for information on the internet, bringing down cover art, actor/actress/director data and so on (it sometimes gets it wrong, though, in which case you can edit it). Go to your TV, switch to Roku, select the DS Video channel and you'll be presented with an attractive visual catalogue of your videos (see the screenshot above). You can scroll through the catalogue, sort it alphabetically, by genre, producer, actor and so on. It all works very well, far simply and more consumer-friendly than playing about with Plex or Twonky or the other home streaming solutions.
In addition, Roku have an app for Android and iOS. This lets you control your Roku using a smartphone or tablet, plus adds other tricks such as streaming music and photos direct from your phone to the TV.