Miniature roses grown in the house are pretty much doomed. Essentially they are temporary decoration unless you have a very cool, very light room for them. They are merely small versions of the big hardy rose bushes which live in your garden and they need to be grown outside to thrive. Outdoors they’ll lose their leaves over winter and return in spring.

When you asked about the white spots I gave the same reply. The fact you are still experiencing problems backs up my answer.

Floral posted exactly what I was going to say. Plants that grow naturally in temperate climates - like mini roses, hydrangeas, azaleas and even the little tabletop Christmas trees so popular at this time of year - make very poor houseplants. They simply cannot thrive in the low light, high heat, low humidity environment of an indoor setting. And indoors they are not exposed to the temperature changes that induce vernalization and therefore flowering nor are they able to enter dormancy. A plant that botanically goes through a natural dormancy period - like roses - will not survive for very long without one.

@floral @gardengal, thank you for your comments and information! However, these answers do not directly address my question—being an attempt at a diagnosis of the yellowing of the mini rose's yellowing leaves—but indirectly point to the inhospitable environment of the miniature rose being situated indoors, which I will admit is a non-neglectable issue for this plant. Still, what I do seek here rather than how the plant is doomed is how to nevertheless take the best care of it within this special given condition—hence the reason for my specifying that the plant is indoors and tagging this post in the house plants forum.

Therefore, did you mean to recommend that I should never have purchased this plant in the first place, knowing that I do not have a garden to place it in outdoors (had I had a garden, would I still have to winter this rose inside, being in zone 7)? If so, I do agree with you. I will not purchase another such rose for indoor purposes in the future.

Thus, I do now consider this here an experiment to see whether such a popular plant sold from department stores and nurseries can indeed survive indoors, so as to provide helpful information for future growers who would like to have their indoor mini roses—however they are obtained—live longer into the future.

Sadly, a great many essentially unsuitable plants, especially flowering ones, are sold to the unwary as house plants. For those who are happy to enjoy them temporarily, and have no regrets about slinging them in the bin when they die, this is fine. But people like you, who are interested in plants and actually want to garden are going to be disappointed unless you can provide indoor conditions very unlike the average domestic interior. If you were happy to place your rose on the windowsill and then live with the windows wide open all winter it would be delighted. It is not evolved to grow and be green all winter. What it really wants to do is relax, drop its leaves and doze until spring. My dd was given one of these and it languished in her flat. I advised her to stick it out on the balcony. It has thrived out there for three years now.

@gardengal @floral: Thank you for the advice! I now understand that the yellowing foliage is likely due to stressful growing conditions, so will adjust the conditions as best as I can manage for now. I will take care from now on to provide this miniature rose with as close an environment to the outdoors as my indoor conditions allow and give it plenty of light and cooler air. I’ll see how this goes and also look for any opportunity for bringing this plant outdoors, now that I know it can withstand colder weather than I had previously expected. There might be an update on how this goes on this forum. Thanks for now!

QZ we don’t know where you are located but if you have cold winters it’s a bit late to put your rose outside. If you have mild winters and can find it an outdoor position introduce it very gradually and don’t be surprised if the leaves fall off.

Good info from gardengal and floral uk.

I especially liked floral uk's :

It is not evolved to grow and be green all winter. What it really wants to do is relax, drop its leaves and doze until spring.

Somewhere here on GardenWeb is a document describing in detail how to keep a miniature rose in reasonably good health indoors, but I can't quite locate it. If any of you remembers where to find it, please include a link.

QZ:

It is almost certain that the leaf yellowing you are seeing is a result of multiple stressors the rose is experiencing in your home. That's not your fault - its simply a fact that the rose was grown in a greenhouse, and is now faced with trying to acclimate to dramatically different conditions (IE: lower light levels, much dryer air, etc).

Now, its not impossible to keep the plant in good health in the home, but there are several challenges that need to be overcome. Most importantly is the light intensity issue: on the average winter windowsill, roses are getting a small fraction of their optimal light levels. This alone can result in dramatic leaf loss. The only remedy for this is to supply additional lighting. Commonly, people use compact fluorescent bulbs, or (these days) LED plant lights. If you are just lighting one small plant then you can likely get away with buying a single bulb that can be used in a standard light fixture. Some of the smaller plant lights are quite inexpensive and come as an all-in-one fixture + bulb configuration. At this point, you have to decide if you want to invest in the technology for a single plant. Only you can make that assessment.

A cool windowsill isn't necessarily the worst thing for a miniature rose. As long as the leaves don't freeze, and as long as daytime temps are at least 65F or warmer, you're in the acceptable zone.

A major obstacle to rose growing indoors is insect pests. The worst/most common are Spider Mites. It is almost inevitable that you will get Spider Mites on the undersides of the rose leaves, so you need to be ready to deal with that. (You can Google "spider mite damage on roses" or similar, to find photo examples of the issue) Spider Mites love hot, dry air, so if you can maintain some humidity where the plat is, you'll have less of a battle on your hands. Your best (and cheapest) weapon against Spider Mites is water: simply take the plant to the sink once or twice a week and hose off the undersides of the leaves with a strong spray of water. Mites hate water and they are easily washed off, so if you wash the plant regularly, you can potentially avoid the Mite problem entirely. Its easier to avoid insect problems than fix them once they've happened.

The HGTV article linked here is a brief-but-reasonable document that explains much of the same info in greater detail:
https://www.hgtv.com/outdoors/flowers-and-plants/trees-and-shrubs/grow-a-miniature-rose-indoors

I expect you will find that the rose will continue to drop yellowed leaves over the next few week. It may in fact lose all its foliage. That's not unheard of as the plant goes into a semi-dormant state, sensing that its light source has diminished to unsustainable levels. If you should find yourself with few or no leaves left, its a good practice to cut the plant down to about half its current height. Given time, it will make new growth, so it might as well start with strong new growth from close to the base of the plant. Cutting it down helps facilitate that. Also, be more sparing with water if the plant does drop most/all of its foliage. A leafless roses doesn't need a lot of water: just enough to keep the soil barely damp to the touch is sufficient. That might mean watering once a week or less. When the rose does decide to resume growth, it will need more water, which you will figure out pretty quickly by observation. Adding a strong light source will encourage new growth also.

Now, it is true that these miniature roses are sold as gift plants, and are considered in the industry to be "disposable" gift plants - much as we regard Poinsettias and the like. That doesn't mean you can't keep the rose going, but it will require some effort and careful attention on your part. It really comes down to you to decide how much effort you're willing to make.

Best of luck, and feel free to ask questions, should you have any.

Paul