While I live in Michigan, I can tell you that roses are party girls - they like to eat and drink. They need about 5 gallons of water a week. If you have been feeding them chemical fertilizers they may be in decline from excessive salts. If you "wash" the soil with a product called Clearex and begin using organic fertilizers, such as Rose Tone by Espoma, alfalfa, and cotton seed meal. Lots of rose growers also use a handful of Epsom salts in spring and again in early summer to provide magnesium. Lack of iron with cause yellowing too. California is rose country so I would chat with folks at a good local independent garden center that sells lots of roses. A soil test is also a good idea before you begin playing chemist. Too much of a good thing can do great harm. Happy Yardening, Nancy.
Roses Flower Sparsely With Yellow Leaf Buds And Stunted Shoots No Pests Observed
Question From: S. Haynes - CALIFORNIA
Q: Old roses (25 years) and newer (5 years) flowered sparsely last spring. Leaves yellowed and dropped off. No growth after that. This spring the leaf buds are yellow, small, stunted shoots (1/2" long). The roses are in a large east facing bed, widely spaced, bark mulch. Have previously flowered well. No insects observed, no galls. Can't figure out the problem.