I don't know what varieties you have in the states, but over here we have two main 'wild' types - rosa rugosa and dog rose. Rosa rugosa produces big fleshy hips, that tend to be wider than they are tall, and are apparently tastier (not tried either raw, so can't comment). The dog rose is more common in the wild though. Some 'domestic' roses have hips, but not all of them. My mother assures me that all roses that produce hips are edible, but that the flavour varies. I wouldn't like to swear to it though!