One store is on its way, and another is "chasing" a spot in one of Roseburg's largest retail centers.That's the latest news from Garden Valley Shopping Center, which has been undergoing renovation to its midsection since last fall. There are three retail spaces -- each about 15,000 square feet -- being prepared for new tenants.The center, at 780 N.W. Garden Valley Blvd., has Ross Dress for Less and JCPenney Co. as anchors.Moving into the mall's center space this summer will be The Dollar Tree, a Chesapeake, Va.-based retailer.Rumors of a Michaels arts and crafts store coming to the mall have …