Perennials tolerant of Dry Soil
Try some of these selections in your rock garden! Sure there is Thyme and sage and oregano...but check out these for ideas...
Achillea (Yarrow)
Amsonia (blue Star)
Anthemis (Golden Marguerite)
Armeria (Sea Pink)
Artemisia (Wormwood)
Asclepias (Butterfly Weed)
Aurinia (Basket of Gold)
Baptisia (False Indigo)
Belamcanda (Blackberry Lily)
Chrysanth. parthenium (Feverfew)
Coreopsis
Dianthus
Echinops (Globe Thistle)
Euphorbia (Spurge)
Gaillardia (Blanket flower)
Geranium (Cranesbill)
Helianthus
Heliopsis
Hemerocallis (Daylily)
Iris 'Pacific Coast Hybrids'
Kniphofia (Torch Lily/Red Hot Poker)
Liatris (Gayfeather)
Limonium (Statice)
Oriental Poppy
Rudbeckia (Black-Eyed Susan)
Salvia (Sage)
Sedum (Stonecrop)
Solidago (Goldenrod)
Stachys (Betony)
Thermopsis
Tradescantia (Spiderwort)
Yucca

And how about a few Drought Tolerant Grasses?:
Andropogon (Bluestem)
Cortaderia (Pampas Grass)
Elymus (Blue Lyme Grass)
Festuca (Blue Fescue)
Miscanthus (Eulalia Grass)