I started by rolling out some fondant and cutting out small circles - I just used one of my piping tips to cut out the circles.
Grab a circle and start smashing it a little with your finger tips. Especially around the edges. This will make them thin and they'll curl under a little.
Roll the first circle around itself.
Start adding more circles on one at a time (after you've smashed up the edges a bit). You can use a dab of water to help them stay if they aren't sticking well.
I used 9 petals for most of the flowers. But pretty much just keep adding until you think it looks good. I didn't take a picture of just one rose finished. But here is the cluster of roses I put on top of my neices birthday cake. I'll post a picture of the completed cake and some instructions for that soon.