Roth to coach Gremio for fourth time
Roth, who earlier this year was sacked by Gremio's arch-rivals Internacional in the southern city of Porto Alegre, replaced Julinho Camargo.
Camargo lasted only a month since his appointment after Renato Portaluppi resigned.
The 53-year-old Roth, tasked with lifting 15th-placed Gremio away from the danger of relegation, signed a contract until the end of the year. He also had spells at the club in 1998-99, 2000 and 2008-09.
Only five of the 20 first division clubs have not changed coach at least once this year through dismissals or resignations including Brazilian championship leaders Corinthians and second-placed Flamengo.
Atletico Paranaense, with Portaluppi now in charge, are on their fourth coach in eight months.