I had a similar problem and solved it by buying metal screw in stakes. I bought them in Klondyke I think it was around £5 for 4. They are around 1.5 inch wide, slightly curved for strength and around 18 inches long, with a point at the end. This allowed me to attach them (holes provided for screws or nails) and hammer them in quite far into the soil.
I would like to add that I don't think that was the job they were intended for but they done the trick!
Alternatively, if you have any off cuts you could make wooden stakes and attach them. Some log edging have longer ends with a point on it, I take it that this wasn't what you bought.
Hope this helps.
Angie

Attach it at the back to wooden stakes and drive them in deep pulling the roll tight as you go.

or get some tent pegs perhaps .