I used a canvas size of about 400 x 300 on a transparent background.

I went to "File" "Preferences" "General Program Preferences" and clicked on the "Transparency" tab and changed the colors to a darker gray so I could see what I was doing better.

I used the airbrush with the settings below and a rose color #C58480 to paint the rose around the middle of the canvas.

Shape = Round
Size = 32
Hardness = 25
Step = 1
Density = 100
Opacity = 80

Add a new layer and change your color to a darker shade, #AF5957 and change the Airbrush settings to match the settings below...

Size = 32
Hardness = 25
Step = 1
Density = 60
Opacity = 55

And use the selection tool, ellipse with Anti-alias checked, to make a selection like the one shown below and dab on the darker color with your airbrush.

And repeat the same to add some shading on the bottom with the same color.

CHanging to a much lighter color #E1BCBB I dabbed some highlights on the rose on a new layer and then changed the airbrush size to about 5 I added some little dots on the top.

Ok I made all the petals on seperate layers, I used a lighter color #F3E1E1 and the airbrush with these settings

Size = 35
Hardness = 25
Step = 1
Density = 70
Opacity = 55

And made an ellipse selection again and used the airbrush to dab on the lighter color, Here are a ton of screenshots showing you each petal....

On a new layer at the very bottom, I used #837D5B and the airbrush with the settings below to paint the leaves

Shape = Round
Size = 15 (smaller size for the little leaves)
Hardness = 25
Step = 1
Density = 100
Opacity = 80

And then changed the airbrush size to 2 and the opacity to 35 and used a darker green to paint some details on a new layer, used a gaussian blur of about 1 on this too.

Add some vines using the same settings.....

Add some highlights and shading to the leaves using the same settings you used for the petals and you are done :o)