Sonoma County is giving a company a nearly 15-million-dollar construction contract for work on the planned Tierra de Rosas development in Roseland. Santa Rosa-based Ghilotti Construction Company will build sewer lines, utilities, streets and other infrastructure. The full Tierra de Rosas development is expected to cost 40-million-dollars. It will include a one-acre public plaza, a 24-thousand-square-foot civic-use building and a food hall or “mercado.” It will also feature 75 affordable and 100 market-rate housing units.