About 200 police officers swooped into camps in the working-class districts of Aubervilliers, Stains and Saint-Denis, officials said.
The raids came after a probe by the children's protection wing of the police service, launched last year, said minors were being "ill-treated and forced to beg" under threat of violence.
Officials said dozens of cellphones stolen from passengers on underground trains were found in the camps.
The network was responsible for "75 percent of pickpocketings on the Paris metro", according to officials, and was was also connected to a money-laundering racket in Romania.
The French government is trying to get an estimated 15,000 Roma, most of whom live in makeshift camps, to return to their countries of origin, mainly Romania and Bulgaria. But the continuation of the previous right-wing government’s policy by the Socialist-led government has aroused criticism by rights groups.
Romania, one of the two poorest countries in the European Union, has the biggest Roma minority in Europe: 620,000 according to the latest official census; more than two million according to local rights groups.