Answer: Roses transplanted in midsummer will undergo a certain amount of adjustment period which can cause a gap in blooming. These roses also rebloom depending on their overall health and growing conditions, so transplanting can cause them to stop forming new buds for at least a while.
In the meantime, keep the soil slightly damp like a wrung out sponge, not saturated/sopping wet and not dried out. Using several inches of organic mulch in a flat layer over the root area will help keep the soil cool and moist between waterings. When you water, water slowly and thoroughly so it soaks down to the deepest roots. To know when to water, check the soil with your finger. If it is still damp, do not water yet.
Fertilizing would ideally be done on the basis of soil tests. (Your county extension should be able to help with the testing and interpreting the results.) However, a spring application of compost as well as applications in early spring and early summer of a general purpose granular or slow release fertilizer such as 10-10-10 per the label directions should be sufficient. The organic mulch will also help feed the soil as it breaks down slowly over time.
With a newly planted rose, I would suggest a top dressing of good quality compost only (no fertilizer) at this time. Do not fertilize in late summer or fall as this can encourage late season growth that does not have time to harden off before winter.
In late fall, after frosts have occurred, mulch generously over the root area with an organic mulch. These should be winter hardy in your area without additional protection assuming they are grown on their own roots rather than grafted. If in doubt, your retailer should be able to tell you.
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