It would be better to keep a mini in a container in zone 4, that way you can move it indoors(by a window) during the winter. They might survive the winter on your porch or patio if it gets enough sunlight.

So with that said I would be safe to plant them in Zone 5 A where I live, I always ask that question for that way there is no question about things living in Zone 5 A.

I fact I like to have plants that will grow in Zone 4 knowing that they will survive in Zone 5 A. These last two Winters have been very cold.

Always better be safe than sorry.

Once you plant the Miniature Roses how long does it take for them to get established?

I feed my roses alfalfa meal and they do very good. Any comments are welcome.

In zones 4 and 5 you need to protect ALL roses in winter. Minis are no different. Most minis are own root roses so if planted deep and protected well they should come back from the root ball even if the tops die back.

Like any other roses minis take about 3 years to reach maturity. Because of your cold zone though they will never be as large as they could be because of winter die back.