The darker the sugarpaste - and hence the more food colour paste you have used - the softer it will be, and harder to mould. So, for your first attempts, use pale colours. (Using liquid food colour may make it too soft.) Once you have kneaded and coloured the sugarpaste you may need to adjust the texture: if it is too soft, add a little icing sugar; if too dry, add a tiny amount of white vegetable fat. If possible, colour the sugarpaste the day before you need it, as it will be much easier to work. Store sugarpaste in a sealed polythene bag, and finished roses in a cardboard box (not an airtight container or they will sweat), both at room temperature. Never keep them in the refrigerator. Sugarpaste roses will keep for months.
Mould 7 or 8 balls (to become the petals) from the remaining sugarpaste and lay them on one side of the bag. Fold over the other side on top and flatten each ball until quite thin. The thinner it is, the finer the petal, but don’t be too ambitious at first.
Very gently peel back the polythene. Take a petal at a time and, with the side you pressed on uppermost, mould it around the cone, completely covering the top. Take the second petal and place it centrally over the seam of the first (again, with the side you pressed on uppermost), moulding it around the cone. Place the third petal directly opposite. Tweak out all the petals as you work, to look like a real rose. You have now made a rosebud!
Fold the remaining 4 or 5 petals around the rosebud in the same way, each overlapping the last. Again, tweak out these petals as you work. With a small knife, cut away the base at a slight angle. You can use these offcuts when you make the next rose.