The first thing you need to do is let them ripen. It takes 90 to 120 days for a rose hip to ripen and the seeds mature. The hip should turn yellow, orange or red.
Next step is to get them out of the hip and clean them very well. You need to scrub off all of the hip material. That material has an enzyme in it that deters germination so you need to get it all off. Don't be afraid to really scrub the seeds hard. They are very hard and you won't hurt them by scrubbing. I like to use a small metal sieve and rub the seeds hard against the sides to clean them.
Some people stratify but others just plant them right away. I do stratify mine in damp paper towels in the refrigerator. I leave them for about 4 weeks and then start checking them. A lot of times some have already germinated in the paper towels. Germinated seeds go into seed starter trays and under lights. When they get two sets of real leaves I plant them up into cups to get more size. Here I do mine in the winter so I keep them inside under lights until it's warm enough outside to put them out in full sun.
I know some people have special beds and do plant them right in the soil to germinate but I find I can't keep track of what's what when I do that. The seed starter trays let me label everything well.
Sprouting time depends on the variety and seed. I have had some sprout in a few weeks and I have had some that didn't sprout until the third year I stratified them!
If a rose is a repeating rose you should get bloom the first season. I have had first bloom in as little as 8 weeks from germination. If a rose is a once bloomer it may take from 3 to 5 years to have it's first bloom. They usually need to build up a frame work of older branches to get their first bloom since they bloom on old wood and not new wood like the repeaters.