Montgomery County Executive Charles W. Gilchrist yesterday nominated Lewis T. Roberts, a veteran county employe, as chief administrative officer. Roberts has held the job, the No. 2 job in county government, on an acting basis since April.

The appointment of the 49-year-old Roberts, an assistant CAO since 1973, requires County Council approval before he can officially take over the $67,000-a-year job of overseeing the government's daily operation.

Gilchrist said he never really looked at anyone else for the job and was only testing Roberts the past three months.

Announcing the appointment at an informal luncheon with reporters, Gilchrist also said he expected to see a collegial, "cabinet government" style of decision-making in the remainder of his second term. Roberts' appointment is an essential part of that new style, Gilchrist said.

Roberts, a low-key bureaucrat with a thick white mane and easy wit, contrasts sharply with the man he replaces as CAO, Robert Wilson, who resigned after Gilchrist's reelection last November.

Wilson was the quintessential "Beltway bandit," a professional manager who moved frequently, holding the top appointed jobs in Fairfax and Prince George's counties, and then Montgomery.

Roberts, on the other hand, has been with the Montgomery County government for 30 years, starting out at 19 as a part-time draftsman for the planning commission. He moved up to become deputy director of planning and finally moved to the county administrative office.

Where Wilson was often called a hard-edged professional who made many enemies during his four-year tenure in Montgomery, Roberts is seen as more relaxed.