Go ahead and get snippy with your roses. As long as you are doing the pruning before the middle of August the roses should be fine. The heavy pruning with loppers that take the roses down to 3 foot stumps  should be done in early spring when you see daffodils blooming in your area. Using hand pruners to cut back the longest canes in summer will encourage more late summer and fall blooms. Cut back to a joint or node shortening the canes by up to two thirds of their length. Them feed and water well. Keep growing, Marianne Binetti