I think the point Charlie is trying to make is that selective colour is one of those techniques that's often not used to best advantage. Because it's actually quite easy to do, and can produce relatively dramatic results many people try it. The intent of selective colour is to draw the eye to one specific aspect of a scene, for instance in a commercial, the bulk of the scene might be monochrome, but the featured product, say a box of cereal is in full colour. This grabs the viewer's attention and makes it very clear what he/she should be looking at.
With your rose image, my suggestion would be revert the background foliage to colour again but to desaturate it slightly so that the bloom clearly stands out, but the image as a whole doesn't look so unnatural.