FORT WORTH, Tex. — Leather Factory Inc. here said it has completed the acquisition of Roberts, Cushman & Co., a New York-based maker of hat trims, for $5 million in cash. Leather Factory has stated it expects Cushman’s 1994 sales to tally about $6.2 million. The combined companies should post sales of about $40 million in 1995, Leather Factory said. Leather Factory distributes leather, leatherworking tools, buckles and belt supplies, shoe-care products, leather dies and trims for belts, bags and apparel.