Most miniature roses grow on their own roots instead of being grafted on to different rootstock. So, while it is not often done, it is usually quite easy to increase the number of your plants by division just as you would with chrysanthemums, daylilies, etc.

In the spring (it can also be done in the fall), look at the form of your miniature rose. It will most likely have more than one stem emerging from the ground at the base of the plant - often there are several. Sometimes there are even low growing branches that have lain on the ground and taken root - they root easily from branches and stems. (The latter can be cut off from the main plant, dug from the ground, and replanted separately - be sure the base and roots are planted well underground.)

If you find that your miniature rosebush DOES have more than one basal stem, dig up the rose bush and cut it apart, making certain that each new section of the rosebush will have adequate roots on it. Prune the tops of the newly separated plants back rather heavily, prune off any broken roots, and replant just as you would a new miniature rosebush. If each section is planted deeply enough so that two or more of its branches are growing from underground level, these branches or stems will eventually develop roots, ensuring more new rosebushes in future years.