Shaping bushes may not seem so important for you right at first. It will become so as your bushes grow and mature. Many modern roses are vigorous growers, and they have to be kept within bounds if landscaping is a consideration. As you know, rose wood comes in three sizes. Basal breaks, or main canes, are the largest and grow from the bud union.
Laterals develop on canes, and stems grow on laterals.
Split bark is a sign of wood that probably must be removed. These openings, which are usually caused by stems rubbing against each other, are breeding grounds and entry spots for diseases. Creamy white or green, with no brown spots, is healthy. Brown or blackened wood is very old or dead and won't produce blooms. Fresh wood is much easier to cut than deadwood, and you'll learn to feel the difference with your shears.