Some roses grow one bloom per stem but others produce many blooms per stem. It is a function of the rose variety that you are growing. Nothing to be concerned.
Because of its age, I would not consider pruning yet. The American Rose Society suggests that pruning start after the plant is 4 years old. And the simplest method usually consists of pruning the top 1/3 of the plant in winter, getting rid of stems that cross or that are dead as well as opening the middle a little so air and sunlight can get in there and minimize black spot. I said "usually" because there are some roses that bloom once a year and those should be pruned after they bloom in Spring. This time of the year, they may be busy developing flower buds for Spring so pruning now would cut Spring 2012's blooms.
So, do nothing this year and look around for rose books so you can read more on pruning. You will find there are probably 14,213,945,822.1 recommended ways to prune! YOu can also do searches on the Internet; do a find on "pruning roses". But bring a tall cup of coffee. You would be surprised as to how many hits you get.