One rose hip may contain up to 12 differently sized and shaped rose seeds. As roses have been hybridized for centuries, each rose seed may be a throw back to any one of its ancestors. Hence, it is possible to plant 12 seeds from the same rose hip and get 12 different plants.
Note that seed raising can be difficult and rose seeds can take up to 2 years to germinate.
However, if wishing to try one’s hand at this, here is how to go about it:
It is best to sow into a pot filled with either compost or seed raising mix of your choice, water well, then seal the pot inside a plastic bag to create humidity. A small stake in the centre of the pot will keep the plastic bag upright, preventing it from falling onto small seedlings when they emerge. When sealed, place the pot in a shady spot in the garden. Check the pot ocassionally for signs of germination.