THE ARTIST who drew the Nov. 9 cover of The New T Yorker -- a strong and affectionate portrait of two vintage Manhattan office buildings done in plum, cherry and dusty rose -- is Roxie Munro, a painter who had always thought her work too assertive for that magazine but who in fact had already sold it 25 of those small bottom-of-column "spots" and who has another cover coming out soon, for which reason she is somewhat concerned about upsetting her modest relationship with The New Yorker, considered by many the Impossible Dream of illustrators ("I never even thought about doing a cover till this year, when I began coming in for the weekly art conference; they're so sensitive there, they let me see the proofs and argue with them over cropping because I'm a very careful composer and a quarter-inch means a lot -- they even reject me sensitively, and it's always my best ideas that they buy"), because if she had her way she would live entirely on her own large paintings, now selling at up to $2,000 and soon to be featured in a Delaware Art Museum show, plus what she sells to the magazine, thus getting her out of the hectic life of courtroom artist for newspaper and television, a life of long days sitting on hard benches and sketching judges and scenery in preparation for the frantic work on a 10-minute sentencing, to be completed in a taxi, on the subway, at stoplights (on a plane, even, asserts her sister Ann Munro Wood, also a courtroom quick-sketch): "a weird little business, but exciting, with maybe only a dozen full-time pros in the country doing it," in the further pursuit of which dream she is moving from D.C. to a nearly assured New York loft and becoming yet another Washington artist who has been lured to the vortex of the American art cyclone ("all that artists do up here is talk strategy: real estate and surviving"), perhaps the natural culmination of a climb that began 30 years ago when, at age 6, she won a countywide art contest, still a delicious memory in "a sweet small-town childhood" on the western shore of southern Maryland, and that continued through an oceanographic phase at the universities of Maryland and Hawaii to self-discovery as an artist ("I remember the day, and I'm so thankful it came when I was only 20") at Ohio University graduate school and, paralleling the climb, a growing power of concentration which enables her to think about her work constantly, even while commuting to Washington or to her place at St. Michael's, Md., "and not to have my life cluttered up with a bunch of personal garbage," as she puts it, a concentration that has given her, despite the brisk walk and quick, certain movements, the fast talk, the bright, observant artist's eyes and electric alertness, a sense, not at all of nervousness, of hecticity, of being driven, but -- amazingly, yet somehow . . . rightly -- of serenity.