It's an easy task to harvest and store seeds. Open the ripe hip with whatever works best for you, scissors, a small knife, whatever you want to use. Remove the seeds and rub the fibers and any hip tissue from them, then place in small plastic bags with the label recording the cross, and store it in the refrigerator until ready to plant.
Once you are ready to plant rose seeds, you'll need something to plant them in. Of course, you can use pretty much anything you have handy and want to use, but if you have many seeds to find soil for and experience some more extreme heat and aridity issues, something along these lines may be just "what the doctor ordered".
I wanted something I could protect against slugs, snails, rabbits, rodents, squirrels and the birds who love to dig up seeds and unearth seedlings. I also wanted a method of permitting them to grow outdoors in full sun without having to worry they would dry out and fry quickly. Because I have to allow them to continue growing in the seed tables all summer until the weather is appropriate for me to transplant them individually, and clean out the tables for the next crop of seeds, I wanted something with sufficient soil to hold enough water for many vigorous seedlings at one time, particularly over the hotter, drier months.
I also wanted something readily available and at "friendly cost". Browsing my local "home improvement store" yielded the idea of using fir fencing boards. They're 8" wide and available in 6' and 8' lengths. I could also find very green, wet boards, making them easier to keep watered as the wetter wood seems to draw less water from the soil due to evaporation. Fortunately, the store will cut the lumber for you, so I didn't even have to break out the table saw to put them together. I decided on the 6' boards. For fencing use, they have sculpted tops, which I have cut off to square the board. Then, I have them cut two boards into four foot lengths, leaving the remaining lengths (not quite two feet long) for the shorter sides of the boxes. At the local prices, each box cost about $7.
To prevent the soil from washing through the bottoms, I selected nylon window screen, which is easily cut with ordinary scissors. To support the window screen, I used plastic hardware cloth, which is also easily cut with scissors. Staple the screen across the table form bottoms and trim the excess, then staple the plastic hardware cloth to them and remove the excess. Because the short sides aren't quite 2' long, for support under the hardware cloth, I bought an inexpensive package of 2' wooden stakes used to mark property lines, sprinkler lines, etc., and screwed them to the bottom of the table forms.
The tables are set on saw horses with 4' lengths of 2" X 4" placed between them. The boxes are then placed on the 2" X 4" supports where the cross pieces made by the wooden stakes space the screen bottoms off the cross supports so they don't remain constantly wet, making them last longer.
Earlier versions were all too short, requiring me to lean over to plant and remove seedlings from the tables. These new tables were placed on taller saw horses, and, with the extra height provided by the cross supports, I can stand erect and work the tables so there won't be the usual back aches due to their previously too-short height.
You may use any type of potting soil you wish. In my conditions, I've had great success with moisture control types. This size box holds nearly four cubic feet of soil, depending upon how deeply you fill them. I only left a few inches inside the box for the seedlings to grow under screen cover because once they are a few inches tall, most birds are going to leave them alone.
I found an inexpensive, useful method of separating the rows of seeds. Thin bamboo plant stakes are easily cut with pruning shears, or bundles of them can be cut to fit the tables using a saw.
Now, it's easy to set the seeds in fairly straight rows, placing the plant labels at the beginning of each row so you can easily tell which seedlings belong to which cross. Once they are all set in place, cover with approximately a quarter inch of your potting medium and water in thoroughly.
With any luck, within a few weeks, you should see some new roses poking through the soil surface. The fun begins!