Roses do not like wet feet, therefore good drainage is of utmost importance. Since this bush is planted by a downspout, it undoubtedly is getting too much water. If there is gravel below it, that would be the final nail as gravel does not improve drainage but acts as a reservoir to collect water. Unless you can divert the water from the drain e.g with an extender, the wet conditions will continue as the season progresses and if rainfall continues. This is not the best time to move a rose - after the leaves have developed, even after it flowers. It can be done but it would be risky depending on how warm the temps are at that time. It would be a real shock to the plant. If done, you would have to 'baby' it, protect it from sun, and when dug, remove as much of the root system as possible. At this point, I'd opt for diverting the water away and move the plant in the fall or very early next spring.