Answer: To some extent, this may depend on the varieties you are growing, as some are simply more vigorous than others. However, to be honest, my main suspicion is that they need more sun. Roses need full sun at least 8 hours a day to do their best, with 6 hours spanning noon being barely adequate so that late afternoon to evening sun may just not be intense enough or long enough.
Otherwise, it sounds as though you are already doing most everything right by maintaining a regular pruning and feeding schedule. Be sure to monitor pests and diseases and treat as needed, and deadhead regularly to promtoe vigorous growth. The only other possible exception is the original soil preparation which you didn't describe. (Roses do best with a rich, deep, moist but well-drained soil.) At this point you might try side dressing or mulching with a rich compost or well rotted manure in fall and early spring and maintaining a good layer of organic mulch throughout the year to work at keeping the soil healthy and see if that helps at all.
You might want to run some soil tests designed specifically for growing roses. Your County Extension (Tel. 345-3283) should be able to help you with the tests and interpreting the results.
Another possibility to consider would be trying some of the remontant or other shrub roses since a number of them are more shade tolerant. Good luck with your roses!
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