Allow rose hips to develop by leaving dead flowers on the plant. The flowers are typically pollinated by insects, or pollinate themselves in some varieties, so there is no need to pollinate by hand unless you are breeding specific plants together. Leave the flowers on the rose plant without cutting them. After they wither, small fruits known as rose hips will develop in their place.
Numerous things could be influencing the plant, from soil quality (do you amend and or feed/fertilize it?) to the circumstances of the move. It’s best to transplant roses in spring or ofall, not midsummer. and the new location should have plenty of organic matter/aged manure (these are amendments, per above). And then there’s watering … . So we really can not tell from here.
Black Spot: Rose plant leaves with black spots that eventually turn yellow have black spot. This is often caused by water splashing on leaves, especially in rainy weather. Leaves may require a protective fungicide coating, which would start in the summer before leaf spots started until first frost. Thoroughly clean up debris in the fall, and prune out all diseased canes.