[From The Practical Book of Outdoor Rose Growing, by George C. Thomas, Jr., p. 16: seeds] can only be relied upon to reproduce plants of their own kind when they are taken from original species... hybrids do not come true from seeds,a nd their seeds are only useful for new varieties.
Each rose seed is technically an achene, a fruit containing a single seed. The achenes are contained in the rose hip, which is the mature receptacle.