Roger and wife Jane experimented with the psychedelic drug in 'Far Away Places', with the resulting high leading him to question his marriage and confront his dissatisfaction with his work.
In an interview with Entertainment Weekly, Slattery suggested that Roger's LSD trip was a true epiphany.
"It gave him the assurance that it isn't over. Roger doesn't have to work. He has a lot of money," he explained.
The actor continued: "You could argue he'd be happier elsewhere. But that experience gave him the insight that he's too young to give up. It isn't time to quit.
"He has this experience where the whole world isn't revolving around him. People can be looking at you but they're not thinking about you. To Roger, that's very profound even if everyone else in the world has already thought of that."
Slattery previously said that he actually admires Roger in spite of his "abhorrent" personal choices.
Mad Men recently wrapped its fifth season.
Watch Roger Sterling's LSD trip from Mad Men below: