I stream almost exclusively from the My Cloud to several Roku’s. To stream media you need to have that media in a format that is supported by BOTH the My Cloud and the Roku. Generally for video MP4 will work. There are a number of free video conversion programs, like Handbrake (https://handbrake.fr/) that will encode video to the proper format for playback on a Roku.
To rip a DVD perform an internet search as there are a number of methods to rip DVD’s for local streaming. There is even a way to rip certain DVD’s (unencrypted and certain encrypted DVD’s) using Handbrake. See the Handbrake documentation for more information. Also see this link (http://grandiloquentmusings.blogspot.com/2014/12/ripping-encrypted-dvds-with-handbrake.html) and others that detail how to add a DLL file to Handbrake to allow ripping of certain commercial encrypted DVD’s.
On the Roku you will need to have a channel called Roku Media Player (https://channelstore.roku.com/details/2213/roku-media-player) which should allow you to access any DLNA server, like the My Cloud, on your local network.
Lastly you can input metadata information (cover art, program name, program information) into the MP4 media file that will be displayed onscreen in certain media players like the Roku Media Player channel. One can use MP3Tag (http://www.mp3tag.de/en/) or Media Monkey (http://www.mediamonkey.com/) for example to add or edit that metadata. Again perform an internet search to learn more about metadata in media files.