Pests and diseases: Prevention is the best way to avoid pest and disease problems. Start with disease-resistant varieties, keep plants in healthy condition (well fertilized and well watered), maintain good air circulation, keep foliage dry, and remove any diseased foliage or spent flowers. For Japanese beetle grubs, use beneficial nematodes or Milky Spore (Bacillus popilliae). Rose Rx is effective against scale, spidermites and aphids. For more information, see the Pest and Disease Finder.
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.
The next step how to grow roses from seed is to sprout the rose seeds. After having gone through their “stratification” time, take the containers out of the refrigerator and into a warm environment of around 70 F. (21 C.). I do my best to time this for early spring when the seedlings would normally be coming out of their cold cycle (stratification) outside and starting to sprout.
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!
So grandma had the right idea in the first place, and she really did know what she was doing. It has always been fun to start roses from cuttings. Some people get their kicks by going "rose rustling" in the deserted cemeteries of old and forgotten mining towns. Others just take a twig from their favorite rose and stick it into the ground in their backyard. There is nothing complicated nor scientific about taking cuttings of roses and rooting them to "start" a new plant. There are various ways of taking rose cuttings, so let's tell you how.

Plant the seeds. Some store-bought seeds can be planted immediately. If you germinated your own seeds as described above, plant them as soon as they begin to sprout. Plant with the sprout pointed downward, as this is the root. Lightly cover them with soil, about 1/4 inch (6 mm) deep. Space seeds at least 2 inches (5 cm) apart to minimize competition.[5]

The easiest way to begin experimenting with rose hybridizing, especially for the beginner, is to simply let some of your roses self-pollinate themselves, so they will "go to seed" and set hips. I have found that Playboy, Hurdy Gurdy, Peggy T and Fairhope are some of the easiest roses to set hips, and there are many others. Let the rose hips stay on the rose bushes at least four months before harvesting.   
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.   

I am curious... it seems that you are just supposed to "soak" the cut stems for a week or more in water.... which is mostly what people normally do with cut roses. But whenever I put roses my boyfriend brings me in water, they just fade within a week or so. I'll "feed" the roses with either sugar in the water or with the packet of plant food that comes with them. I'll cut off a small bit at an angle from the bottom of the stem evert day or so. But after a week or so they start wilting and drooping, so at that point I just take them out and hang them upside down to dry.
You must monitor the seedlings as they grow in their new pots for colour, form, bush size, branching, and disease resistance. Roses with weak, unhealthy or unattractive flowers can be discarded. It will take your new seedlings at least three years before they reach maturity and develop into a big bush. However, the first flower can be seen after one or two years.
Choose the pod -- or female -- flower that will produce the seed pod. Remove the petals. Identify the fringe of yellow pollen-producing structures called stamens that surround the central style. Cut the stamens off with small scissors so they will not accidentally pollinate that flower and so that the pollen will be available for planned pollination of other flowers.

Some roses root easier than others — old-fashioned heirloom types often root better than modern hybrids — but don't let that keep you from trying your hand at replicating garden favorites and sharing your love of roses and gardening with family and friends. RootBoost™ and GardenTech® brands are here to help you learn and succeed in all your gardening projects, so you can experience all the joys of gardening.
Allow rose hips to develop by leaving dead flowers on the plant. The flowers are typically pollinated by insects, or pollinate themselves in some varieties, so there is no need to pollinate by hand unless you are breeding specific plants together. Leave the flowers on the rose plant without cutting them. After they wither, small fruits known as rose hips will develop in their place.
The Baggie Method: This was the first method I ever tried. Here you fill 2-inch plastic pots with potting soil, insert the rose stem halfway inside the pot, then put the pots into a one-gallon plastic zip-lock bag. You can get four 2-inch pots into each gallon bag. I didn't like this method because it caused many of the cuttings to rot since the bags tended to fold over and therefore prevented the air from circulating. The success rate of this method is not very good. It may be helpful to place a couple of small sticks inside the bag to help keep it upright and full of air.
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]
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] 

When pruning, be judicious. If you prune too hard in autumn, plants can be damaged beyond recovery. Instead, wait until spring, when plants begin to leaf out for the new season. (Roses are often not the earliest plants in the garden to respond to spring’s warming temperatures, so be patient.) Give the plant time to show its leaf buds then prune above that level.