Question
Recently I purchased some long stemmed freshly cut roses and placed them in a vase with water, as usual. That was March 1st. I just realized that two of the many have new leaves growing. How interesting. How do I actually encourage these to become rooted roses? I have only seen this happen once before in the same situation. Thank you for your assistance.

Answer
A florist rose means that it was grown in very controlled conditions in a greenhouse. It could also have been treated with an anti wilt chemical which stops the rose from wilting too soon. This just means that your rose has a couple of strikes against it in regards to making roots. And even if you do succeed in getting it to make roots, it probably will not make it in a normal garden setting.
Now having said all that you can do something and see if you can make it into a rose bush.
Here is a website that explains carefully how to get cuttings to root. These sites are  talking about garden type rose cuttings whereas yours are a florist and not fresh, but the routine is basically the same. I have never come across a site that tells you how to try and grow a florist's rose
http://scvrs.homestead.com/cuttings1.html
Before you start cut about one inch off the base of your rose because there could be bacteria plugging up the stem and then cut off the flower head also. It might be a wisdom to get some damp off to make sure the cuttings don't get any fungal problems. Just ask at the garden center for the spray they use when growing seeds.