Answer: It doubtful that the pine needles are the cause of your problem. But to be sure, have a pH soil test done Your county extension agent (301-934-5283) can tell you where to have it tested or kits are available at garden stores if you want to do it yourself. Lime could be added to the soil if indicated.
Are the roses in full sun, or are the trees and fence casting a lot of shade? Is this area near the driveway where perhaps there is asphalt causing some detrimental conditions? Have you prepared the planting holes well with additions of organic matter such as compost? Are you following instructions for fertilizing, and not overdoing it?
Whether it's the pine trees or some other condition, the roses are obviously not happy there. Why not put them in another spot in the yard and try something else against the fence? If you'd like other ideas, post another question with more details about the growing conditions of the area in question.
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