This plant has been doing well up to a few weeks ago.
White leaves sounds like a bad case of Powdery Mildew. Powdery Mildew is a fungus that attacks rosebushes foliage and new bloom buds at times. The very best fungicide I have found to knock it down and get rid of it is called Green Cure. Green Cure comes in a white powder form in a plastic container. There is a measuring scoop/spoon in the container. Add two scoops/spoonfuls of the green cure powder to each gallon of water in a sprayer. Shake it up well, then spray all the foliage down well with the product. Follow up in 5 to 7 days with another spraying. Use the same timing until the powdery mildew is gone. Green Cure is available for purchase at Amazon.com. Here is more information on it for you: http://www.greencure.net/
Here is a link to an article I wrote on various diseases roses can get and how to deal with them for you as well: https://www.gardeningknowhow.com/ornamental/flowers/roses/rose-bush-diseases.htm
Should Sunblaze Mini Rose (Autumn Sunblaze) be cut back after a branch blooms?
To keep your mini rose blooming, yes you need to deadhead her. Deadheading is removing the spent blooms on a plant. On my mini roses I prune the spent blooms and their stems back to the first cluster of leaves. New growth emerges and new buds as well.
You can wrap the rose loosely with a large towel and place a large trash bag over it at night. The towel insulates it from the cold and the plastic bag prevents moisture from getting the insulating towel wet. Any similar form of protection against the frost is fine. There is no need to prune at this time.
I need help with my miniature rose, it look so sad, a lot of leaves dropped and just looks like might be dying. Noticed a couple new leaves but it has lost about half of its leaves. It is indoors and in a pot (of course). HELP PLEASE.
This is common for miniature roses, they do well for awhile, but when the shorter days of fall arrive, they decline. The best option is to plant them outdoors.
How long do miniature roses live for
Roses renew themselves by sending up new canes from the crown and the crown itself renews itself by spreading sideways in all directions. Thus, a rose can live as long as it receives proper care and the environment is suitable for it. There are some non-miniature roses that are over 100 years old. Most miniatures have no scent but several do. A large number of them is produced by Kordes (Netherlands) and are called Kordana Roses. It is not possible to tell the following before purchasing miniatures in florist stores but, some miniature roses may have been treated with a growth retardant hormone to keep them small so, once you plant them outside, they become larger plants with the same size of blooms as before.
My indoor mini rose plant has started looking bad. When new leaves grow at the top of the longest green stem, they turn brown after only being open a day or so. I can still see new growth coming but it continues every time the leaves open. I have it in a bright place in my kitchen, so it seems light is ok. I have used Miracle grow plant spikes for food once a month. It is not over watered. The base of the plant going into the dirt is still green, so it appears healthy from that perspective. I have no idea why it won't stay looking good. I am not a novice gardener but this puzzles me out. Please help!
They need full sun if you can supply it near a window. I think it may be getting too much fertilizer and possibly too much water. When indoors, plants need less water than outdoors. Roses need a cold period in winter if you have a room that stays colder than the others. It's very hard to grow mini roses inside. If you can plant it outdoors, that would be ideal.
General reasons for leaf browning include: not enough water, environmental stress, root bound, spider mite infestation or nutrient deficiency. Roses perform better when they get more than 6 hours of direct sun. Although the location may appear bright, it may not be enough to sustain chlorophyll production at -for example- summer levels now so you may see foliage dropping for lack of enough sun. You should water it well and then allow the top few inches to dry out before watering again. During periods where there is no active growth, it is not necessary to fertilize. The plants may have winter injury if exposed outside to overnight temperatures near or below 40°F.
While miniature roses can survive temporarily indoors, long-term indoor life is not recommended. It is difficult for them to get sufficient sunlight, humidity, etc. A grow light may help; check with local stores.