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.
After the rose seeds have soaked overnight, rinse them in a strainer and place them into the blender with at least a cup of plain purified water (making sure all seeds are covered), and turn it on for a few minutes. It usually doesn't chop up the seeds, but rather, it will clean off the pulp remaining from the rose hip, which would otherwise mold if left on the rose seed. You may see a few seeds chopped up, but those usually aren't viable anyway. Flush the rose seeds again through a strainer using fresh purified water.
Water. Irrigate roses deeply but infrequently, applying water directly to soil using soaker hoses or drip irrigation. Water needs vary based on weather and soil, so check soil with your finger. Water often enough to create consistently moist soil – not overly wet, not bone-dry. To prevent diseases, keep foliage dry, especially if you must water late in the day.
The Misting Method: As you get more sophisticated in your rose propagating methods you may eventually want to set up a misting bench. It can be an open-air bench or one enclosed in a greenhouse, or even a small misting box, similar to the one my husband Bob built for me. (Refer to "How We Made Our Misting Box," from Rose Ecstasy. You could choose to rig it up with a manual or an automatically-timed mister, whatever your time, money, or expertise will allow. I am fortunate to have a very handy guy for a husband, who is a good sport whenever I come up with these crazy project ideas.
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.