I just can't see an extra wide one staying up. The original poster is
talking about at least 64 inches wide and preferably 96 inches wide.
Add the weight of a quality decorating fabric and your average no sew
velcro is just not likely to hold up. I've never had good luck with
the sticky back velcro.

A 1" square of velcro, epoxied to a brick, and the other half epoxied
to a wall, will hold the brick.

You certainly wouldn't have to use sticky-back velcro... half could be
epoxied or stapled to a piece of wood that was attached to the wall with
screws or nails at the studs, etc. Still, 96" wide roman shades are going
to be heavy to adjust.