MONTREAL — After years of “dreaming” and expansion, Rona has hired a tough veteran from Canada’s grocery industry as chief executive to help it rebuild the embattled home improvement retailer to profitable growth, the company said Tuesday. Robert Sawyer, 59, will become Rona’s president and CEO next month after more than 30 years in grocery retailing, including nearly four years in the No. 2 management position at Metro Inc. (TSX:MRU) — another large Quebec-based national retailer. Rona (TSX:RON), which has its headquarters in the Montreal-area community of Boucherville, Que., has grown to nearly 30,000 employees across the country through a combination of acquisitions, partnerships and internal growth.