Before Roger Marzulla started his new job earlier this month in the Justice Department's Land and Natural Resources Division, the division was flooded with rumors.

The most frequent was that Marzulla, who had succeeded Interior Secretary James G. Watt as president of the conservative Mountain States Legal Foundation, was a rabid anti-environmentalist who would secretly take his marching orders from Watt.

But the 35-year-old California lawyer is not the ideologue many expected.

"It's erroneous to assume I'm any sort of politico," said Marzulla, who is serving as a special litigation counsel. "I'm a lawyer. I have no policy-making responsibility, I'm not even running a bunch of people . . . . I'm quite a babe in the woods wandering around on my own."

He is open about the fact that he is a conservative, but he describes himself as a "classic conservative," and not a member of New Right.

"I believe in the individual . . . as the cornerstone of this nation. I believe in the rule of law. I have no problem with the fact that some of the laws I may be asked to enforce in this position may not be laws I would pass if I were in Congress," he said.

Marzulla, who headed Mountain States for about 18 months until he left last August after differences with its directors, has never met President Reagan or Attorney General William French Smith. And he has never worked in a political campaign. He was hired by Assistant Attorney General Carol Dinkins, who heads the lands division.

Dinkins has said Marzulla will be one of several special lawyers handling high-priority cases in the division, which deals wwith legal issues ranging from environmental and hazardous waste laws to federal land issues and Indian affairs. The division also handles cases for the Interior Department and the Environmental Protection Agency.

Because of his connections with the Mountain States group, Marzulla's appointment was greeted by protests from environmental groups. The Wilderness Society, which monitors the federal government's supervision of public lands, was among them.

Peter Coppelman, who used to work in Marzulla's division and now serves as counsel to the society, said, "Mountain States Legal Foundation has been a fertile training ground for attorneys who oppose the federal government's environmental program. It is an inappropriate place to look for guardians of the nation's resources, as Secretary Watt has proven."

The Denver-based group was formed in 1977 to counter groups that were using the courts to expand the government's role in environmental policy and other areas. It describes itself as devoted to fighting "excessive bureaucratic regulation and the stifling economic effects resulting from the actions of extreme environmentalist groups and no-growth advocates."

Marzulla has said he will disqualify himself from any case in which there might be a conflict, adding that he has "become impatient" with the attacks by environmental groups.

"Once you're a professional lawyer, you take your oath very seriously. I will enforce the laws. And they can watch over my shoulder to see if I'm doing well," he said.