About 12,000 Roh supporters, many holding candles and chanting slogans, protested peacefully near the National Assembly parliament building and the headquarters of the main opposition Grand National Party. Riot police stood ready.
Most people gathered in Seoul, but there were smaller protests across the country, police and media said.
Yun Hee-yun, a 23-year-old college student, said she had joined a crowd police estimated at 12,000 near the National Assembly parliament building and headquarters of the main opposition Grand National Party in Seoul out of pure anger.
"I was so upset," she told Reuters. "As I was born in 1980 the last presidential election was the first election for me and I feel like my vote was totally ignored."
Roh was elected president in December 2002 on a wave of support from mainly young voters who saw in him the chance for generational change in a deeply hierarchical society.
President Roh's fate will be
decided by Constitutional Court
His fate is in the hands of the Constitutional Court, which must rule whether to overturn or uphold the vote within six months.
"I can't believe it," said 57-year-old Kim Kwang-ran. "We had the most democratic and most reformist president in history and the opposition with its archaic elements has pulled him down. I can't bear it."
All Roh's powers are in limbo until the Constitutional Court rules on the vote.Until then Prime Minister Goh Kun will run the country.
"The world is watching us with anxiety and concern," Goh told ministers.
South Korean financial markets reacted sharply to the historic vote, which took place as members of parliament brawled and wept. Burly plainclothes guards had had to prise grimacing deputies' hands off the speaker's microphone.
"This is the day our nation's democracy died"
Investors sought the safe haven of bonds, shares closed at a five-week low and the won shed 1% against the dollar.
Finance Minister Lee Hun-jai sent 1000 letters to international agencies, global banks and fund managers to reassure them that the economy would remain stable.
The economy is just emerging from a downturn and the nation faces parliamentary election on 15 April.
"This is the day our nation's democracy died," said the pro-Roh Uri Party that had sought to block the vote with a sit-in. Its members of parliament said they would all resign.