Use rocks instead of mulch only around plants that have a high drought-resistance. This includes many trees, shrubs and cacti, but excludes many flowers. The drought-resistance of a plant is generally listed on its information tag.
Build a border wall around the plants that you want to mulch with rocks. A border wall prevents rocks from getting spread into undesirable locations, such as driveways.
Layer rocks to a depth of 1 to 2 inches around the base of newly established plants to ensure that they don't receive too much heat and lose too much water at night, which may prevent the plants from growing. Layer rocks around established plants as high as the edge of the border wall to achieve the look that you desire.
Water plants as usual through the rock mulch. Apply the water over the rocks and it sinks down through the rocks and into the soil.