heres what i would do with a horrible looking rose bush which had 3 main stems.....

take one stem and reduce its hight by a third...take another and reduce its hight by two thirds...take the last stem and cut it as close to the ground as possible...do all this after the middle of february.
make the cuts if possible just above an outward facing dormant bud...if none are showing look for a horizontal line across the stem showing where a leaf once grew (the dormant buds are formed just above the place where a leaf stalk meets a stem).

if this treatment is successful new growth will break out below the areas where you made the cuts....now heres the best bit...each subsequent year after mid february cut the tallest of the 3 stems down to ground level...after a few years the oldest wood in your bush will be no more than 3 years old and you should have a bush furnished from top to bottom with flowers.

the above really applies to hybrid roses which is what the chances are yours is.

treat with an all round organic feed if you wish at the begining of march but only sparingly at first building up as the growing season progresses then easing off after midsummer

good luck !