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.
To get the best success, yor rose seed will need a period of stratification (a cold period of about 6-12 weeks). Its a good idea to time this so that it coincides with when they would naturally start to grow in spring – probably around early March, depending on weather conditions. I would look to sowing them in late November/ December and popping them outdoors or if we have a mild winter then stick them in the fridge!
I too, have tried the cut rose flower method, but haven't yet been successful--perhaps because there are chemical additives that the roses have soaked up, or because there are no nodes (which are the points where new shoots grow out), or because the stems have spent much of their energy producing the flowers...BUT, perhaps if the flowers were immediately cut off and some rooting hormones applied to the bottom cut ends, that may work.
The plant will become dormant—and you want it to stay that way; it is the natural state. After the first deep freeze, put is in a room or place (garage) with no heat and natural light (window). You can add some water occasionally but this is not intended to be “watering”; the plant is dormant and will not take it up but the soil can be lightly moist. Bring the plant back outside when it shows signs of coming back to life. Plant it, per the guidance above, when the soil warms.
Prune the roses. Pruning roses keeps them both beautiful and healthy. The goal is to clear away crowded areas to open up the bush, which helps prevent rotting and disease. The pruning strategy differs according to the season, but the cut you make is always the same: prune just above a bud eyes, the areas where branches form. They look like small circular swells and are usually located above a set of mature leaves. Make a down-slanted cut on an outward-facing bud eye.
Rose propagating methods have changed over the years, from the simple own-root varieties of the Victorian era, and progressing to the budded hybrids of the 20th century with its many options of exotic understock such as Rosa multiflora, Dr. Huey, Manettii, and Fortuniana. Now, rumor has it that many of the modern hybridizers and commercial growers are interested in returning to the simplicity of yore. Today's commercial rose growers are finding that budded roses are just too labor-intensive and expensive to produce. Because of this, it appears that we can look forward to more own-root roses being introduced and sold at our local nurseries in the future. Own-root roses will eliminate suckering and hopefully will eventually help to eradicate mosaic virus.
Español: cultivar rosas usando semillas, Italiano: Coltivare le Rose Usando i Semi, Português: Cultivar Rosas a Partir da Semente, Русский: вырастить розы из семян, 中文: 用种子种玫瑰, Deutsch: Aus Samenkörnern Rosen ziehen, Français: faire pousser des roses à partir de graines, Nederlands: Rozen kweken uit zaad, Bahasa Indonesia: Menanam Bunga Mawar dari Biji, العربية: زراعة الورود من البذرة, Tiếng Việt: Trồng hoa hồng từ hạt, 日本語: バラを種から育てる, 한국어: 씨앗으로 장미 기르는 방법