Completely black out room with roller blinds, how?

Del2005

I've a south facing living room with patio doors and a window and I'm going to get electric roller blinds for them as I work shift so half the time my current curtains are open/closed at the wrong time, I'm also thinking of getting a projector so would like for the room to be completely dark.

I fitted blackout roller blinds in my bedroom but no matter how I fitted them some light always got past so in the end I used system which Velcros to the window frame. I know if I just install the blinds that some light will seep past so I was thinking to do them like the security shutters in a shop and have the blind running in a channel but I can't find these on any site I check. I thought it was cassette but after watching a companies installation video they aren't.

What should I be looking for to get roller blinds that run in tracks so that I can completely black out my room?
Thanks

Dr_Colossus

Came across this video some time back and blinds look good, run in a channel as you said. Supposed to be expensive and not sure if that varieties can be motorised but he has all the links in his video.