Forbes Magazine, on 13 December 2000, referred to Roth as having "engineered some 16 acquisitions while putting the pedal to the metal internally to transform Nortel from a simple telecom equipment provider into a global brand name identified with the Internet." 
"We were a slow company and we had to work very hard to become a fast one," says Roth, who began his tenure as CEO with a letter to employees in which he told them the time had come for the century-old company to "get off its duff" and join the new economy 
Time Europe, on December 25 2000, noted that "The change [in Canadian government policies] marked the triumph of ideas forcefully argued by the most successful businessman in modern Canadian history: Nortel Networks CEO John Roth, 58. Mr. Roth warned that 'the country (Canada) risked becoming a second-rank economic power unless it changed its wealth-crimping tax policies and supported high-tech winners (like Nortel)". Roth urged the government of Canada to provide "better tax treatment of stock options", saying, "Policies and business strategies that worked well in the industrial era are a recipe for stagnation and decline in the new economy."
Roth invested heavily in optical technology which was seen as the key infrastructure technology for the new network.
When Nortel’s share price on the Toronto Stock Exchange began a plunge that wiped out the life savings of many investors, Roth argued that Nortel's dominance reflected a failed industrial policy that sheltered enterprises from global competition. "We desperately need to create a culture of winners," he declared 
With the collapse of the Internet Bubble Nortel stock price collapsed. Nortel had been transformed into a large optical company to supply a market that never existed. Market capitalization of Nortel Networks declined from $398 billion to less than $5 billion, and more than 60,000 people were laid off by the company. Roth was criticized after it was revealed that he cashed in his stock options for a personal gain of $135 million in 2000 alone.
He is currently living in retirement in Orangeville, Ontario, Canada.