Answer: Roses grow best in a full sun location with good air circulation. They need soil that is deeply prepared, and amended with ample amounts of organic matter such as good quality compost, leaf mold, or well aged stable manure/bedding mixture.
In a heavy soil you may also need to add some coarse builders sand or fine grit to improve the drainage, and/or plant on a slight slope, and/or use a slightly raised bed.
Using an organic mulch year round, spread in a flat layer several inches deep over the root area but not touching the plant, will help keep the soil evenly moist, help keep down weeds, and also help feed the soil as it breaks down slowly over time.
Proper planting means loosening any encircling roots at planting time to avoid rootbound plants; this is important because these will be stunted after planting.
The soil should be kept evenly moist yet be well drained, meaning damp like a wrung out sponge with a good ability to hold both water and air. It should not be wet or saturated, it should not be allowed to go bone dry either. To know if you need to water, pull aside the mulch and dig into the soil with your finger. If it is damp, do not water yet. When you do need to water to supplement rain, water slowly and thoroughly so it can soak down deep and encourage deep rooting. After watering, wait a few hours and then dig down to see how far the water soaked in; sometimes this can be surprising. It is better to water deeply less often than to water by sprinkling lightly every day.
Once you have provided all of the above, you would run some basic soil tests to determine if and when fertilizing is necessary. Fertilization is ideally done based on test results. This avoids over or under supplying nutrients, neither of which is good for the plants, it also allows you to take into account the soil you are working with. Overfed plants will be soft and weak and subject to pest and disease damage, they may also be less winter hardy. Fertilizer salts can build up in the soil and cause damage to the roots, over fertilizing can "burn" your plants. Also, excess nutrients leach through the soil or are carried away in runoff and cause damage to our ground and surface waters. Roses are not actually terribly heavy feeders, so in general a spring and early summer application of a complete granular or slow release fertilizer with an analysis of 10-10-10 or similar should be adequate. Read and follow the label instructions.
In my experience, most roses fail to thrive because their basic requirements are not being met. Fertilization is only a part of their care. Proper siting, proper soil preparation and planting technique, selection of varities suited to your local climate, and proper pruning all contribute at least as much as to their vigor. I hope this helps you trouble shoot.
Q&A Library Searching Tips