Question
I have tea roses in my garden and I'm having problems with 4 of my plants.. they have only bloomed once and i have noiticeed several with yellow and black leaves I'm not sure what i can do for either problem please help me..

Answer
Your roses have a very common fungal rose disease called black spot. The spores of black spot float around in the air and when it rains or is windy, they are forced to the ground. If they land on a rose leaf then they start their life cycle by pushing their roots below the surface of the leaf. When they have killed that part of the leaf that is when you see a black spot. Too many spots on the leaves will kill the whole leaf and it will go yellow. Good success has been attained by gardeners using a dormant oil spray in the spring before the roses leaf out. Then you will kill the spores that have over wintered on the canes. The weather does have something to do with this disease as fungus like damp and humid condition to grow well. There are also certain colours which are farmore prone to black spot than others, such as scarlet reds, apricots and yellow.  
You can also start to spray with any rose fungicide such as Funginex or Bayer's disease spray, just as the roses are starting to leaf out then you kill the spores that have over wintered on the canes. Spray weekly for a month and then just once a month and you will see a big difference in your roses. Starting to spray when you see black spot is too late to save those leaves but if you spray now weekly with a fungicide until there are no more spots it will keep it under control.