As Canadian environment minister in the early 1980s he faced off with the US government over the cross-border issue of acid rain at a time when the Reagan Administration was denying its existence.
Roberts led a strong public information campaign on both sides of the border that, at one point, resulted in the US justice department officially branding a National Film Board of Canada documentary Acid from Heaven as "foreign country propaganda".
The campaign is credited with ultimately leading to a bilateral accord on acid rain being signed later in the decade.
[6] Roberts ran to succeed Trudeau at the 1984 Liberal leadership convention, coming in fourth behind John Turner.
Roberts led the Canadian delegation to the 1998 Lisbon World Exposition (Expo 98) in Portugal and which lasted from May 22 to September 30, 1998.