In 1955, Drew's successor as Premier of Ontario, Leslie Frost, elevated Roberts to cabinet as attorney-general.

Early in his term, Roberts supported strengthening the Fair Accommodation Practices Act to require restaurants and bars to serve all customers equally, regardless of race or ethnicity.

Kelso had delivered a report that declared organized crime was virtually nonexistent in Ontario; the position was widely ridiculed and likely led to his demotion.

"In Canada," he had written, "there's nothing that can be likened to the Mafia, an organization that in Italy was dismantled long ago by Mussolini."

Roberts came under particular criticism when the press reported that he and officers of the Ontario Provincial Police had communicated with organized crime syndicates in Canada and the US.