If you plant seeds of a rose (other than a species rose with no other varieties within pollinating distance), you won't get the same variety from the seeds. If you want more Angel Face from your plant, you'll need to grow it from cuttings (slips).
In general; rose hips can be collected when they are ripe, shown by a change in colour. The outer part contains a growth inhibitor, so it's best to remove the seeds from inside it. They do better with a cold winter, so if you can't provide that, you may want to put them in the vegetable crisper of your fridge for a month or two. One option is to put them in a plastic lunch box (with lid), with seeds arranged on a damp sponge (can fit several layers in the box). The seeds can be planted about 1cm down in sandy or seed-raising potting mix (no fertiliser) in late winter. A broccoli box is traditional (here) but not obligatory! Don't use heat. A local rose society would be able to advise you, especially about whether fungicides are needed, how often you'll need to water, and when to start feeding the plantlets. In general, the ones that are going to be repeat-flowerers should flower in early summer.
(I'm basing my comments on zone 9, where we'd put the box in filtered sun/shade).