One roll for something like 4-10 pedals depending on pedal size. I used one roll for 6 pedals. Sticks ok when you handle and move your pedalboard aroud with some care. Shake it around and heavy pedals drop off. Once I left my pedalboard side up position for couple of weeks and in that time few heavy pedals had slide down few centimeters. Glue between the velcro mat and pedal stays a little "soft" so you could remove the velcor without a fight, but it also allows heavier pedals to slide a bit if board is positioned "wrong" for longer times. There are other similar products that have some serious grip, but those are more expensive and this does the job for me good enough.
I am using this hook and loop tape in conjunction with a pedal train 2 pedal board. The tape is used to affix medium weight pedals and a few heavier units such as a wah wah pedal and power supply. The adhesive used for the tape is very strong which is reassuring as thisis just as important as the hook and loop side. Be certain you are happy with the positioning of the tape as once applied and 'gone off' it will be particularly hard to remove. I recommend enduring all surfaces are clean before applying the product to ensure the strongest bond possible.