Roger S. Aaron, who as a longtime partner at the law firm Skadden, Arps, Slate, Meagher & Flom helped orchestrate some of the biggest mergers of the past several decades, notably the unions of Exxon and Mobil and Alcatel and Lucent, as well as Daimler's sale of Chrysler to Cerberus Capital Management, died on Saturday in Manhattan. The cause was cancer, a spokeswoman for the firm said. Throughout his nearly five-decade career as a top adviser to the country's biggest corporations - his client list included General Motors, Pfizer and Time Warner - Mr. Aaron cemented a reputation as a trusted adviser to blue-chip companies. Along the way, he built up one of the industry's top merger practices. As a member of the avowed "Young Turks" who joined Skadden in the late 1960s, Mr. Aaron helped build the firm from a small but scrappy legal shop into a sprawling global empire with thousands of lawyers. His cohort of colleagues learned at the right hand of Joseph H. Flom, the pioneering deal-maker who drove Skadden's rise, principally through mergers and hostile takeovers. "He was a person who brought extraordinary passion to all of his pursuits," Eric J. Friedman, Skadden's executive partner, said in a telephone interview. You're talking about someone who for 40 years was on top of the deal world. Roger Shaw Aaron was born on May 15, 1942, to Hyman L. and Phyllis Aaron, and grew up in the prosperous Cleveland suburb of Shaker Heights. He graduated from Dartmouth College in 1964 and earned a master's in business administration from Dartmouth's Tuck School of Business the following year. While a law student in 1967, he spent a summer working at Skadden, then a small firm with ambitions to compete - if not beat - the city's older white-shoe firms. Despite having offers from a number of bigger rivals, Mr. Aaron chose to work at Skadden, becoming the firm's 19th lawyer. On his first day as an associate, he was placed in an office with Peter A. Atkins, another Ivy League graduate who passed up other job offers to work with Mr. Flom. Mr. Aaron and Mr. Atkins formed a deal-making pair that helped Skadden grow rapidly and become a model of the modern law firm: an assemblage of high-powered specialists spread around the globe, providing advice in more than a dozen areas. Mr. Aaron quickly became a member of Skadden's next generation of leadership, establishing a reputation as a quiet but intelligent negotiator who eschewed the flash of other deal-makers. For more than two decades, he headed the firm's corporate practice, serving as a counselor to corporate boards on a wide variety of issues. Within the industry, Mr. Aaron was known for devising unusual solutions for clients" problems. When G.M. sought to buy H. Ross Perot's Electronic Data Systems in 1984, Mr. Aaron helped create a tracking stock, which allowed the automaker's new acquisition to trade independently of its parent. Tracking stocks have since graduated from legal curiosities into established corporate practice. Within Skadden, Mr. Aaron became a mentor to generations of other lawyers. Colleagues remembered him showing up for work at 7 a.m., after having often put in time at the gym, and working until 11 p.m. Outside of the office, Mr. Aaron was known for athletic pursuits like downhill skiing, tennis and golf. He also supported Dartmouth and Yale Law School, and had served on the boards of the American Jewish Committee, the Legal Aid Society and Teach for America. Mr. Aaron, who had homes in Manhattan, Scarsdale and Aspen, Colo., is survived by his wife, Virginia; their sons, Peter and Todd; his mother, Phyllis; his sister, Caroline; and two grandchildren.