If its a newly planted tree ( as in last year) just shape it back into a ball shape. If you ever get a rose bush always cut off two-thirds..no matter what size. The ideal time for pruning is now! When spring arrives its important to feed them. Stay away from Miracle Gro, it leaves a salt build up and will cause soil problems. If you can find a company called Espoma...they have great rose food. Epsom salts ( very sparingly)will bring out color in the petals and a slight acidic soil will make your neighbors jealous of your roses.
Boo, here's what I learned in my Master Gardener Class... Rose Trees are Hybrid roses that are grafted to look like a tree. They need to be taken care of just like regular roses, but because of their unusual shape they need to be pruned differently. Early Spring is the time to prune them. Make sure you use a sharp shear as to not tear the cane. Hold the shears at a 45* angle 'away' from the center of the rose, allowing air flow, which reduces chance of disease. Remove any canes that look dead. A healthy cane will have a greenish cast to the bark and a white pith on the inside... Cut away from the dead part of the cane until you come to the healthy part of the cane...remove any canes that are not 'pencil width' thick. These canes are not strong enough to support the new blooms. Remove woody old canes as close to the trunk as possible. Remove any 'sucker' canes that grow beneath the buds...prune 1/3 in away from the cane. Work towards a balance. Uneven pruning will result in an uneven distribution of weight. Hope this helps you some. Roses are fun to grow and can be addictive. I am more into the new Knock-Out varieties now the past few years....;)