Lots of roses can be grown from seeds actually and will be like parent plant unless they are hybrid or mutation. Hybrid gene sometimes can be vary, stable like either parent or as something else. Grafting is combination of a strong growth rose as rootstock with small prefer growth rose, but just like any grafting, the rootstock gene will emerge the gene with the grafted twig/bud and will always want to grow their own shoots from crown or any higher point. How high the soil or mulch is not the point but would help the new shoots of rootstock to grow.
Very popular grafted roses are the tree form ones. Some very nice roses is very difficult to be propagated by cuttings or seeds so grafting is a way to multiply in short time for market needs.
