Kevin Roche, a Pritzker-winning architect who emerged as one of corporate America’s leading designers during the postwar boom years and became an architect of choice for the Metropolitan Museum of Art and other major institutions, died March 1 at his home in Guilford, Conn. He was 96.

His son Eamon Roche confirmed the death but did not provide a specific cause.

The Irish-born Mr. Roche moved to the United States in 1948 and became a protege of Eero Saarinen, the Finnish American architect known for designing sculptural, futuristic buildings. For nearly a decade, he was Saarinen’s principal design associate, absorbing his expressionistic style and his philosophy that architecture should serve a higher purpose by bringing people together and helping to build a sense of community.

After Saarinen’s death in 1961, Mr. Roche and colleague John Dinkeloo spent years overseeing the completion of their employer’s unfinished work, including Dulles International Airport near Washington, the Gateway Arch in St. Louis and the TWA terminal at John F. Kennedy International Airport in New York. They then went into business as Roche-Dinkeloo, keeping the name after Dinkeloo died in 1981. Their guiding principle was the reimagining of giant work spaces and museums, trying to make them more appealing to the toiling or visiting masses.

In 1965, Mr. Roche completed his first major commission: designing a home for the new Oakland Museum of California. He and Dinkeloo conceived of a plan for a three-tiered building that was stacked like a set of stairs, with each level opening up to gently sloping terraces, lawns, and trellis-clad walkways. Viewed from above, the museum itself disappears and only the geometric gardens are visible.

In 1968, Mr. Roche unveiled his design for the Ford Foundation headquarters in New York. Twelve stories of glass-walled offices look out over treetops and a lush conservatory — an indoor garden oasis in midtown Manhattan that to this day remains open to the public.

Although soaring, plant-filled atriums would eventually become a cliche, introducing a burst of greenery to a declining New York City felt bold and uncommonly generous at the time. New York Times architecture critic Ada Louise Huxtable deemed the building a “splendid, shimmering Crystal Palace” and a gift to the entire city.

After creating a master plan for New York’s Metropolitan Museum of Art in 1967, he spent four decades adding on new galleries, including a glass pavilion, reminiscent of an Egyptian pyramid, that houses the Temple of Dendur.

Other wings of the Met were renovated to provide better traffic flow for the rapidly growing crowds. In the parts of the museum that Mr. Roche overhauled, massive skylights bathe the artwork with natural light, and sloping glass walls allow visitors to look directly out to Central Park. The lines are crisp and modern, contrasting with the classical formality of the original Beaux-Arts building.

Hired by banks, insurance companies and manufacturers, including General Foods and Union Carbide, Mr. Roche designed vast, light-filled work­places that inspired comparisons to spaceships and came equipped with amenities such as fitness studios and hair salons.

Detractors of Mr. Roche’s style contended that some of the monumental buildings he designed could feel forbidding and unwelcoming because of their vast scale and blunt geometry.

The New Haven Coliseum in Connecticut, a hulking arena completed in 1972 as part of an ambitious urban-renewal scheme, was widely criticized for being built to a scale better suited to the monster trucks that occasionally faced off inside the stadium than to the humans in the surrounding community. In 2007, the city demolished the concrete-and-steel structure, a job that required more than one ton of dynamite.

As the architect for the Knights of Columbus inter­national headquarters in New Haven, which he finished in 1969, Mr. Roche took inspiration from towering grain silos. He even used silo tiles to decorate the four concrete cylinders placed at each corner of the 23-story glass tower that dwarfs almost everything in the vicinity.

Although his work is generally associated with late modernism, Mr. Roche steadfastly refused to be categorized or labeled throughout his six-decade career. In 1982, he was awarded the Pritzker Prize, considered the profession’s equivalent to the Nobel Prize. “Kevin Roche’s formidable body of work sometimes intersects fashion, sometimes lags fashion, and more often makes fashion,” the jury noted in its citation.

Mr. Roche “reinvented the museum, and reinvented the office,” said Eeva-Liisa Pelkonen, an associate professor of architecture at Yale University and editor of “Kevin Roche: Architecture as Environment.”

“Kevin was an architect who made bold speculations, and oftentimes they came with a big risk, or a big reward,” Pelkonen said. “Sometimes they worked and became classics, and sometimes they backfired. So I think the verdict is still out, but there’s no question that he belongs among the most successful, and most significant, architects of the 20th century.”

Eamonn Kevin Roche was born in Dublin on June 14, 1922, and grew up in Mitchelstown, in County Cork. His father was a cheesemaker who gave him his first commission as a teenager: designing a piggery for the family’s farm. Mr. Roche went on to attend University College Dublin, which had Ireland’s only architectural school at the time.

His instructors were largely concerned with passing down the hard-boiled conventions of Beaux-Arts architecture, but Mr. Roche was drawn to the pared-down minimalism that was being pioneered by architects such as Ludwig Mies van der Rohe, whose work he had come across in magazines. After finishing his degree in 1945, he moved to London and found a job with Maxwell Fry, one of the first British architects to renounce the classical style in favor of modernism.

Mr. Roche’s fascination with Mies’s architecture led him to enroll in a postgraduate program at the Illinois Institute of Technology, intending to study with the star architect. But he stayed for only one semester, having found Mies uncommunicative and aloof.

Broke and unemployed, Mr. Roche landed an interview with Saarinen. Their first meeting was inauspicious: Mr. Roche’s cousin, actress Kathleen Ryan, had recently arrived in New York on a Hollywood expense account, and the two had gone on “a tremendous binge for about a week,” he later told the Irish Times. After staying up all night at the Stork Club, Mr. Roche drowsed off midway through the early-morning interview. Saarinen gave him the job anyway.

As his reputation grew — he received an American Institute of Architects Gold Medal in 1993 — Mr. Roche designed university arts centers, corporate campuses and federal sites including Station Place, a 1.6-million-square-foot complex connected to Washington’s Union Station that also serves as headquarters of the Securities and Exchange Commission.

Survivors include his wife of 55 years, Jane Tuohy Roche; five children; and 15 grandchildren.

Mr. Roche continued practicing architecture well into his 90s, cutting back to a four-day week when he turned 95. In a 2016 interview with Monocle 24, he argued that most people chose to retire only because they were stuck in unfulfilling, dead-end jobs.

“They’re not energized by what they’re doing,” he said. “Whereas I am energized very much by what I am doing all the time, and very excited about it. And I think it’s a great opportunity on two levels. One is to be able to make a contribution to the environment, and the other is to satisfy your creative desires. To create something, sculpturally or visually, that’s attractive and interesting and beautiful.”