You will need:
I've chosen some good photos of roses, taken by me in full sunlight, where the blossom and the bud as well as some leaves can be seen in all their details.
With a pen, I draw a pre-sketch of all main forms of the rose, the bud and all leaves. As a pattern, I use theprints of my photos or the computer screen, whereI can enlarge all details. For an easier recognition of the tonal value (light-dark-contrast) I use the black and white print.
Here you can see the whole composition with first glazes. The basic tint for all green mixtures is Greenearth, one of my favourite greens. It is a transparent colour and one of the most natural green shades one can find and use even in pure form. For the red of the blossom/bud I basically use Quinacridone red light, Saturn red and Perylene darkred. For the petals, I mainly use the very useful for botanical painting colours Titanium yellow and thetransparent Yellow orange, which can be partially mixed with Transparent orange and Cadmium yellow lemon.
For a more three-dimensional effect, where the bud seems to be more in the foreground, it gets the most intense colours. The white denticulated edges at the leaves of the bud will be left open. At first,I paint the red glaze with indicated smallest teeth. After drying, I paint the green glaze at the oppositeside with small teeth, too.
Now I paint the first glaze of the leaf in a cooler Viridian to let the bud come forward. This leaf later will get more glazes in warmer green shades. The denticulated edges will be painted with the brushtip in growing direction. The middle vein will be leftopen - it will be painted with a tender glaze only afterfinishing the leaf.
Here, nearly all petals and leaves and stalks are painted. For the reddish shimmering edges ofthe leaves I add some Quinacridone red light and Transparent orange into the still wet glaze. The green reverted leaf underneath the blossom gets a first shadow glaze, while the saw-toothed edge remains free.
The blossom is nearly ready painted with shadow parts, but nevertheless it needs some more glazing layers. If a colour became unintentionally too dark, you can rewet this part with a small wet brush and take off the colour with a Kleenex. Then, you can paint an even lighter glaze. Into the green leaves I already painted some details in several green mixtures to indicate the inner parts of the typical "pillow-like" forms between the secondary veins.
Here I already corrected the too dark parts inside the blossom. The leaf at the right underneath the blossom got an attractive hard shadow, which shines through onto the underpart of the leaf. For the soft shadows at the underpart of the redpetals you will need several glazes, as otherwise it is not possible to paint convincing shadows on intense red parts. Thus, I glaze with an intensered, mixed to be darkened with a very small part on Manganese violet. This violet contains more red than blue amounts. The delicate thorns at the stalks will be painted with the small No. 2 flat brush and get afterwards a shadow with the finest possible (No. 0or 1) brush at the underpart.