"Fold" it like this, make sure the sides are equal when you're beginning. When you made more roses like this, it's not hard to guess how long it has to be.
Fold one side over the little triangle like thing.
This is what it'll look like from the back.
Then simply just fold the side you didn't fold over the triangle yet, over the side you did fold over the triangle (still get it? :P) so that you'll get a square, keep on doing this untill you think it's enough. Just guess how many you'll need.
Keep on squeezing it together as you fold, so that you won't get lost :)
When you're done, stop squeezing, but hold the 2 ends of the ribbon.
Grab it like this, and pull one of the 2 ribbons. Make sure you dont turn it, the kinda twists need to stay in the rose.
Stop when you think it looks nice, and if you wanna, you can grab a needle and thread to make sure it stays a rose.
It doesn't matter how long the ribbon is or whatever, just try new things :) If you have any questions, just ask me.