To shape the roses, you'll start to add lines that represent the way the petals are attached to the bud.
For the rose to the left, add the swirl at the top to represent the petals that are not yet unfurled. At the midpoint of the circle, add a couple of lines to show where the bud casing opened and curled back.
For the rose on the right, make two sloping triangular shapes that look somewhat like shark fins at the top of each side of the circle. Add short lines curved under the bud to mimic the opening and pulling back of the bud casing.
These lines should still be drawn fairly light, so they can be erased later if needed.