Transplanting miniature roses from indoors to out doors is a temper-mental process. the miniature rose will need to be slowly introduced into the sunlight. Keep in mind that you have to know what zone you are located in.
What you will do is gradually start taking your roses outside and setting them in the shade (not sunlight) not at first. Slowly start setting them in the sun for just a couple hours each day. Watch their leaves and keep them moist.allow a couple of days in the shade then start with the sunlight gradually increase the sunlight.
Upgrade the pot size as your miniature rose starts to grow. Clipping about a quarter inch off the ball of the root, then planting into a larger pot. once the roots have grown down into the larger pot and are wrapping around it is time to transplant your miniature rose into the ground.
the rest is mother nature and you keeping a watchful eye over the miniature rose. Do not use chemical fertilizer as this tends to kill the roots. Try to locate and use an organic mix that is slow acting. Just like children we have to watch every thing that is happening with our miniature roses.
Below is a site that is a community site that will allow any individual to communicate about roses and more: http://www.gardenweb.com/ is very informative.