Leaves can be distinguished by their shapes and also by the ways that they are arranged on stems and branches.
Rose leaves are oval in shape and they have saw-tooth edges. They are borne oppositely on stems, with the exception of one single leaf at the tip. opposite leaves come from essentially the same spot–one going left and one going right.
The leaves of the elm tree are also sawtooted and are similar in shape; but they are borne alternately on the branch.
The leaves of both the rose and the elm tree have a vein running through the middle of the leaf; and other veins evolve from that main, middle vein.