Lisa, I've just looked at the video - I've not seen nor used this frame.
Thoughts -
You would need to be very accurate when pushing the fabric into the slots that it was
absolutely on grain. I see this is a problem especially with canvas.
It's
vitall that the side of the fabric is lashed to the side bars so that tension is evenly applied. As shown the sides would flap.

So... in my entirely personal opinion I would not waste money on this frame.
The correct term for 'Roller' frame is actually 'Slate' frame. They come with lots of different variations; some tighten the side bars with a screw, others need cotter pins. I have both..
But they all have a tape on the roller to sew the fabric to, and strong side bars for lashing.
Attaching the fabric is called 'Dressing a slate frame' - google that to see lots of ideas.
This is a rather long-winded one that I came across.