Ragosa rose transplant
The plant has been growing at the lawn and garden shop for about three years. it had nice roses and buds on it when transplanted. Now the buds are dry and falling off. the leaves are turning yellow. Too much sun? too much water?
Fairbanks North Star Borough Alaska
It sounds like your rugosa rose is experiencing severe transplant shock. Hopefully you have taken all steps to reduce the stress the plant gets from loosing its feeder root hairs and therefore its ability to take up water and nutrients. It can take a number of days to weeks for a plant to grow more root hairs. During this time the plants soil should be kept moist and the leaves should be protected from the evaporative effect of dry air and breezes to keep it from drying out (ie covering with polyspun horticultural fabric ie Remay). Transplanting at the peak of the growing season, when a plant is flowering and fruiting is especially stressful, so shoulder season is best for this. Senescence (dying and dropping off) of flowers, fruits and eventually leaves is normal for water stressed plants.
Water stress can also be caused by overwatering, so proper drainage is mandatory along with careful monitoring of soil moisture content (especially after transplanting).
I would remove all blossoms, fertilize with a complete fertilizer (now, not after August) and make sure moisture is managed, with a focus on helping your plant be strong enough to make it through to next spring.