The thick gray folders are stacking up on Selwa Roosevelt's desk at the State Department, reflecting the large number of heads of state and foreign ministers who are coming to Washington in the next few months.

"A lot of people want to see this president, and those who've been here before want to see him again," said Roosevelt, the chief of protocol, shielding the list from view. There will be "at least 23" major visits by July, plus a few private drop-ins, and only a few names have been announced, she said.

The number is "way above average" for most presidents, she said, but not for President Reagan. There were 102 top-level visits during Reagan's first term -- twice the number for President Carter -- and this year's pace is higher.

As a result, Roosevelt and her 57-member staff are working overtime, filling a gray folder for each visitor with arrangements, reminders, letters, warnings, diets and schedules.

The plans cover every minute from the arrival of the dignitary's jet to its departure. They outline everything from who sits where in the limousines to what kind of flowers will grace the tables at the secretary of State's lunch for 70.

At least that's how the system is supposed to work. Awaiting British Prime Minister Margaret Thatcher's plane at Andrews Air Force Base in a heavy fog last Dec. 21, Roosevelt's group was stunned to hear the plane approach the runway and swoop upward, headed for Dulles International Airport.

"Well, it was five minutes for her to get there but an hour for us . . . so we had to call and have them hold her on the plane, and she'd already been on the plane 19 hours" from Hong Kong. With a police escort, the official cavalcade covered the 45 fogbound miles to Dulles in 35 minutes.

There is protocol in who handles protocol. Roosevelt's office handles "state" visits (by chiefs of state, such as kings and queens who may or may not hold real power) and "official" visits (by heads of government, those who actually run things). She arranges to have them stay at Blair House or in hotels. "State dinners," however, are handled by the White House protocol office.

Roosevelt also takes care of foreign ministers who come to see Secretary of State George P. Shultz. They don't get a state dinner, but all three categories may get lunch and/or dinner with Shultz and/or Vice President Bush. To further confuse matters, there are different procedures for "working" visits as opposed to "private" visits, and spouses have separate events.

Still, the absolute maximum number of people Roosevelt has to provide for in any delegation is 14, called "the official party." They are paid for, pampered, transported, fed and entertained as official U.S. guests. "That is absolutely it because we do the same thing for everybody," she said. "For the official party, we are their nannies."

The rest of the tag alongs, be they two or 50, are called "the accompanying party" and, while they are treated as well as they have requested, they pay for the privilege.

"Our job is to make things go smoothly. Nobody notices us if it goes well, but if we foul up -- well, then it's on the front page," Roosevelt said.