Denis,
that’s a useful link. I’m in the process of building a 4.2m x 3.6m roll of roof so getting suitable wheels and track will be necessary.
Accessories to large gates seem to be one way to go. Besides wheels and track electric gates also supply electric motors and teethed track that allow electrification. Some builders have also used up and over garage doors electric motors and track.
Those wishing track angled or otherwise may like to consider metal stockbrokers. They have very long lengths and various shapes and sizes cut to length and deliver. They are much cheaper that off the shelf DIY
Regards
Eric