Roses aren't quite the dogs of the botany world, but they still have displayed an enormous variety of scent, color and form. Roses are part of the Rosaceae, with over 100 genera and more than 3,000 species. The family is divided into four subfamilies, but whether these groups are well-supported by DNA sequence information is still under some debate. The family ranks up there with the grass (grains) and pea (soybeans) families as the some of the most economically important crops.
The family contains many well-known fruits such as apples, pears, cherries, strawberries, and peaches. They all share a common floral formula, with some of the floral parts (sepals, petals and stamens) fused into a structure called a hypanthium. This shows different arrangements of parts, if you are interested.
Cultivated roses are often bred to be double-flowered, that is they have more petals than their wild ancestors. This phenomenon is thought to arise from mutations that tell the stamens (of which there are many) to develop as petals, which is apparently a "default" structure when other information is lacking.
In terms of cultivated roses, there are Old Garden roses and Modern Garden roses. The Old Garden roses bloom once in a profusion of double-flowered, highly scented blooms, on shrubby, disease resistant plants that are white, red or pink. Modern Garden roses are the result of selection for specific traits, and as you would imagine, the variety is pretty impressive. Within the Modern Garden roses, there are other classifications, such as miniature, and climbing, as well as the more familiar shrub roses. By introducing genes from a wild relative, (Rosa foetida), Hybrid Tea rose breeders were able to develop varieties with shades of copper, deep yellow, even lavender. In an interesting turn of fate, these same beautiful colors also brought along decreased disease resistance and scentless blooms, so they are bred more for color and are considered higher maintenance than other varieties.
Floribunda and Grandiflora roses are popular these days, and combine the best traits of Hybrid Teas with heightened disease resistance and more of that yummy rose scent.
The cut flower industry depends on perfect-looking specimens that often come from far away. As a result, the industry has been perhaps too reliant on the application of pesticides, and you can read about it here and here. I'm not sure if it's marketing or the real deal, but it seems that roses from Ecuador are really popular. Perhaps due to climate and soil, the flowers can be huge! In a great example of the consumer wanting to do the right thing if given the opportunity, Whole Foods and Sam's Club now offer Fair Trade roses from Ecuador. This certification protects workers (mostly women) from excess pesticide exposure while paying them a fair wage; everyone seems to win in this one.
I have two roses bushes in my garden. One's a 10 foot monster that was a housewarming present when my x and I moved into our last house. I wasn't all that concerned about the implications, it was a free rose bush! It has yellow-orange blooms that smell divine and it is about as unfussy as garden plants can get. The other one is a climbing rose I bought last year to grow up the corner of my house and it's got single flowers that are white on the inside and deep purple at the outside. I'd plant more, but I don't have any more room!