Water every four days would usually not be enough for potted roses in hot weather. Water every two days would not normally cause waterlogging in a properly-draining pot. Possibly the roses are just shedding some leaves.

One way to check for drainage is to shove a thin piece of absorbent, unfinished wood-- like a yardstick-- down the side of the pot and hold for a few seconds. A zone of saturation will show as on a dipstick. Normally there will be a small saturated zone at the bottom, or just above any drainage layer if you have used one (not recommended). Allow the pot to drain for an hour after watering and try this. If several inches are saturated, that would suggest a drainage problem.

When leaves are yellowing, starting at the bottom, I check for spider mites. Lynn