By 1979, Roslof had joined Erol Otus, Bill Willingham, Jeff Dee, Paul Reiche, and Evan Robinson as a staff artist at TSR, Inc. in Lake Geneva, Wisconsin. Over the next year, he provided interior art for:
Lawrence Schick's White Plume Mountain (1979)
Gary Gygax's Slave Pits of the Undercity (1980) and Expedition to the Barrier Peaks (1980)
the hardcover rule book Deities & Demigods, in which he provided illustrations of the entire Greek pantheon (1980)
various issues of TSR's Dragon magazine, commencing with issue #42 (October 1980)
Roslof also provided the cover art for some of AD&D's greatest adventures:
Queen of the Demonweb Pits (voted the single greatest adventure of all time, in compilation with the rest of the GDQ series, by Dungeon magazine in 2004)
The Ghost Tower of Inverness (ranked 30th greatest adventure in the same Dungeon article)
Secret of the Slavers Stockade
Keep on the Borderlands (ranked 7th greatest adventure in the same Dungeon article)
The last of these is perhaps Jim's best known work, since the adventure was included in later printings of the Dungeons & Dragons Basic Set, of which over one million copies were sold.
In May 1981, despite the significant amount of artwork needed for an ever-increasing number of company products, TSR manager Kevin Blume fired two of the six staff artists, Paul Reiche and Evan Robinson, on what TSR editor Steve Winter described as "trumped-up charges of insubordination". When Bill Willingham and Jeff Dee complained, they were also fired, leaving only Roslof and Erol Otus as the art department. Roslof was promoted to Art Director, but instead of simply staying with the style of art that had defined TSR products since 1975, Roslof hired a cadre of brilliant artists whose artwork would define TSR to a generation, and who would all go on to successful careers as fantasy artists: Jim Holloway, Larry Elmore, Jeff Easley, Harry Quinn, Keith Parkinson, Tim Truman, and Clyde Caldwell. Parkinson recalled how he was hired: "I drove up one day to see if I could do some freelance work. Jim Roslof, who was the Art Director, hinted that I could join the staff full-time, but I missed the hint. A few days later, I called him about a job, and he had just hired somebody else the day before, but he’d keep me in mind. The next day, he called back, and had an opening."