The bad economy continues to hammer retailers, with The Home Depot the latest to struggle. The home-improvement chain will close its Expo home design store, including the large outlet in Roseville. The Atlanta-based chain will close the 34 EXPO Design Center stores — including four in California — and layoff about 7,000 workers during the next two months. In 2005, the company closed 20 of the money-losing EXPO design centers. Home Depot, once one of the best-performing retailers in the industry and on Wall Street, has been battling declining revenue and profits with the economic downturn. Even with the latest round of store closures, Home Depot will remain the nation’s largest home-improvement chain, with almost 2,000 stores and more than 300,000 employees.