That's a lovely reason!

I haven't deliberately grown a rose from seed. But if I were, I would remove the seeds from the hip, and give them a wash. This is because the fruit is designed so that a bird will eat it and then excrete the seeds at a distance, and some berries contain germination inhibitors so that the seed doesn't try to germinate prematurely.

Then I'd plant them straight away, with just a fine scattering of soil on top - the rule of thumb that you should plant bulbs at a depth equal to twice the diameter of the bulb seems to work quite well for seeds too. I'd make sure the compost was good and moist, then I'd enclose the pot/seed tray in a clear plastic bag to keep the moisture in.

If nothing happened in the first 3 weeks, I'd make sure the compost was still moist, then put the pot/seed tray (still in its plastic bag) somewhere safe outside, and forget about it till next April. Some seeds are triggered by a period of cold - if they germinate in warm weather, they might emerge just in time for winter, whereas if they don't germinate until they've had a period of cold, they're more likely to germinate when the weather is warming up for spring.