Cover the cutting loosely, pot and all, with a plastic bag or plastic wrap and keep the soil moist. Putting a tall stake into the pot will hold the plastic away from the leaves. If the plastic touches the leaves, they remain wet and can succumb to a fungus disease. Along the same lines, make sure the condensation can escape from the plastic or the stem will rot.
as mentioned when I replied to Mick, the powder with be a fungicide as we’re trying to help prevent dampening off – although careful watering is always the best solution to this problem. The hydrogen peroxide mentioned in the blog will be the same as the hair bleach and is just an extra precaution taken by the author to sterilise her seeds. Using normal bleach in tiny quantities is usual practice in preventing harmful bacteria in seed processes, especially if they are prone to disease in the first place.
Growing roses from seed can be challenging, since the majority of seeds you collect often won't germinate regardless of your efforts. Fortunately, most rose plants produce a large quantity of seeds inside their rose hips, so it usually isn't necessary to achieve a high success rate. Keep in mind that the plants that grow may be different in appearance or other characteristics from the mother plant, especially if that plant is a hybrid of two varieties grafted together.
Prepare a large hole. You'll need one for each rose bush you're planting. Use a garden spade or shovel to dig a hole 18 inches (45.7 cm) wide and 18 inches (45.7 cm) deep. The measurements don't have to be exact, but a hole this wide and deep will be suitable for most roses. Mix the soil you removed from the hole with compost, and use some of it to form a small mound in the base of the hole. Add some bonemeal or rose fertilizer.
To start rose bush from cuttings, once the rose cuttings have been taken and brought to the planting site, take out a single cutting and remove the lower leaves only. Make a small slit with a sharp knife on one or two sides of the lower portion of the cutting, not a deep cut but just enough to penetrate the outer layer of the cutting. Dip the lower portion of the cutting into a rooting hormone powder.

As soon as the rose seeds have been removed from the rose hips, rinse the seeds in a solution of purified water (any bottled water will do) with 5% bleach. This would be about two teaspoons of bleach per cup of water. Rinse the rose seeds with plain bottled water in a strainer, then soak the seeds in straight 3% peroxide for 24 hours. CAUTION: Do not mix bleach with peroxide because there could be a chemical reaction.   
Fertilize the roses. After they are established, roses should be fertilized a few times per growing season. Use fertilizer (either liquid or granule) in early spring, when you see the first few leaves sprout. Use it again after the first bloom, and again if there's another bloom. Stop fertilizing the roses at the end of the summer, just before Labor Day.[7]
I would definitely mix in some compost with your garden soil as this will improve the structure of it. The dusting with fungicide is useful as it prevents the risk of infection, however, if you keep an eye on them and be ready to spring into action then it could be worth trying without . As for planting, I would personally keep them inside for a while, give them a chance to strengthen up before putting them outside in the elements!

Fertilizer: Roses are heavy feeders, and will benefit from a steady supply of nitrogen, phosphorus and potassium. You can provide these nutrients with either liquid or granular fertilizers, at a ratio of approximately 5-8-5. In most cases, regular applications of compost, rotted manure, fish emulsion and seaweed extracts will provide roses with all the nutrients they need. These organic amendments also help to moderate pH imbalances and stimulate beneficial soil life. Other organic amendments favored by rose growers include greensand, black rock phosphate and alfalfa meal.