With patience, a rose can be grown from a seed, and indeed all the Peace roses of today are descended from a plant grown in 1939 from a single seed nurtured by Francis Meilland, the hybridizer.
But a random seed from a Peace rose or any hybrid would be unlikely to produce a plant like the one it came from.
As for the time it would take, a wild, unhybridized rose like Rosa rugosa would be relatively quick and easy to grow from seed, with little preparation; in the early fall, remove the seeds from the ripe rose hips, the fruit of the rose, and plant them.
For many other roses, however, the seeds must be refrigerated for about four weeks at about 40 degrees, for what gardeners call stratification, a cold period, and again for about four months, at a somewhat higher temperature, for germination, with a light on in the refrigerator. They can be nurtured in moist peat moss.
Before sprouting, seeds can be tested for viability by seeing if they float in water. Floaters are hollow and unlikely to germinate.
The sprouts from the refrigerated seeds can be planted, preferably in sterile soil, perhaps with a cutoff plastic bottle as a greenhouse.
If they survive, they may produce miniature roses in just a couple of months, previews of the color of mature roses, but not their shape.
The plants and their roses should reach full size in about three years.