Nicholas J. Roll, who is primarily responsible for the daily operation of the Metro bus and subway system, resigned yesterday effective next Jan. 4.

Roll, 55, has been with Metro and its predecessor agencies for 14 years and was for many years the chief of Metro's real estate office. In that role he was responsible for acquisition of all property and rights of way needed for the construction of the subway system.

He almost resigned three years ago to enter private law practice. But Theodore C. Lutz, then Metro general manager, persuaded Roll to accept the job of assistant general manager for transit services -- the top operating post.

In that position, he oversaw the opening of the subway's Blue Line in 1977 and three subsequent extensions to the Blue, Orange and Red lines. He also supervised major changes in the bus network.

Roll's first experience with operations came following the now-famous July 4, 1976, bus fiasco when Metro promised to take thousands of people home from the bicentennial fireworks display, then didn't deliver. Roll was plucked from the real estate office and told to make the bus system work.

Roll said yesterday he plans to do what he intended three years ago -- practice law in Berwick, Pa., his home.

His departure leaves Page with two major unfilled operating jobs: Roll's and the job of director of bus services, recently vacated by T. S. Trimmer.