The Black Plague....of Roses

So yesterday I went outside and discovered that my roses could be doing better, but they aren't.  The roses are small and shriveled and I noticed the stems/canes are black.  I went crazy today and cut all the black slippery stems off and thorned myself on several occassions using some bad language.  I talk a lot to myself when I'm working with the plants and don't realize that I am talking outload sometimes. If only I could see how I look to my neighbors....:)  It must be quite the sight. 

Notice the black canes on the left and the healthy green ones on the right. What is going on?

My sense is that I overwatered these guys and created a fungal disease. Canker?

Here is where you all might have something to say.......

I trimmed the bushes to the ground leaving the main canes shorter and then I moved the irrigation tube. All suggestions were to remove the black canes so that they didn't infect other canes....well that made me cut the bushes severely as a lot of black canes were attached to the main node.  I will put some fertilizer down and this may be a waste of time?  I am new to roses and they are treated a bit differently than some of our other plants....so I'm wondering, am I doing the right thing?  Help!!:)