Answer: Based on your description the bugs are probably Japanese beetles. These are difficult to control, however you may be able to apply a product containing neem (sold at garden centers and nurseries) to repel them. You can also try handpicking early and late in the day when they move more slowly.
The loss of foliage can contribute to poor performance, but roses also need full sun for at least half of the day (including the hour of noon), a location with good air circulation, and an evenly moist but well drained soil, meaning not saturated or sopping wet and never bone dry.
You may need to water them during dry spells. To know if you need to water, dig down and check the soil with your finger. If it is still damp, do not water yet. When you water, water slowly and deeply so it soaks down in and encourages deep rooting. This is better than watering lightly every day. After watering, wait a few hours and then dig down to see how far the water went; sometimes this can be surprising.
Using an organic mulch year round helps keep the soil more evenly moist, holds down weeds, and also helps feed the soil slowly over time as it breaks down. Apply the mulch in a flat layer over the root area, but do not allow it to touch the stems.
You should also feed your roses. In spring and again in early summer apply a top dressing of good quality compost and/or an application of general purpose granular or slow release fertilizer with an analysis of 10-10-10 or similar proportions. Read and follow the label instructions.
This is a low maintenance rose, but you should prune it back each spring by about half its size to remove winter damage and bring it to a somewhat symmetrical appearance. You may do this by cutting individual canes or by simply shearing it off.
I hope this helps.
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