Help & troubleshooting for channels on your Roku device, including adding/removing channels, logging in to, authenticating, or activating a channel, channel-specific playback issues, assistance contacting channel publishers to report issues, and adjusting channel-specific settings.
The Xfinity Stream app will let you access DVR recordings that are X1 Cloud recordings, which may include 'copies' of physical DVR recordings. You will not be able to access any recordings that are only available on your cable box's physical hard drive, if it has one.
To be honest, Comcast's handling of DVR is very confusing under X1, especially if you have a physical DVR. Some recordings may end up being cloud, some only physical, and some may be available both ways.
If you don't have X1, then DVR recording is not available outside of that box.