Humidity

• Miniature rosebushes grown indoors like humidity. During winter months, if humidity drops too low, the bush's leaves will yellow and fall from the plant. Some people use a room humidifier or place the plant's container on a saucer of rocks in water to raise the humidity around the plant. A drop of bleach in the water surrounding the rocks may prevent algae growth.
  
  

Sunlight and Water

• Miniature roses require full sunlight and moist soil. The leaves of plants that are allowed to dry out often turn yellow or fall from the bush.
  
  

Black Spot

• Miniature rosebushes grown indoors or outdoors suffer the same diseases as their full-size counterparts. Black spot (Diplocarpon rosae), a fungal infection, occurs on rosebushes subjected to wet and warm or overly humid weather. The leaves first show black or brown spots, then turn yellow and drop from the plant. Infected leaves of such plants should be removed and the plant should be treated with a fungicide.