I use the MFT dies and a Sizzix die. The Sizzix one is great for felt and other fabrics. If you're on the fence about purchasing a die to make these, I say go for it! They really give a nice finished flower that you just can't get with cutting a spiral in a circle.
I've also used a scalloped circle die and cut a spiral into the die-cut and then rolled it up. That works nicely too, but the dies designed to make the rolled flowers are just easier and give a nicer look, IMO.