Answer: Did you have a very cold night or two? When roses have put out a lot of late fall growth it is not hardened enough to survive cold weather and may react severely to a cold snap. The plant itself should be okay even if the tips look bad. Next spring prune away any winterkilled wood (be sure it is dead!) and wait for new growth.
Roses need as a rule of thumb one to two inches of water a week during the growing season and should be kept evenly moist but not soggy. The water is best applied in one deep soaking rather than frequent light sprinklings. They should also be mulched year round with several inches of organic mulch such as shredded bark. They appreciate applictions of compost and well rotted manure as well as regular fertilization but in my experience the biggest limiting factor to their growth (assuming the soil is at least average) is lack of water, the next most common limiter is usually lack of sunlight.
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