From the ArcaMax Publishing, Gardening Newsletter:
http://www.arcamax.com/news/gardening/s-1900-268927
Question: How do I prune or deadhead miniature roses in order to keep
them blooming abundantly?
Answer: As soon as the blossoms have faded, clip them off just below
the flower with a pruning shear or scissors. This will keep the plants
looking their best and encourage them to send energy into producing
more flowers this summer. In regions with very hot summers, roses may
take a break in mid summer because of the heat, but start flowering
again in fall. Be patient and you'll be rewarded with beautiful
blooms.