Karl-Anthony Towns added 24 points and 10 rebounds for Minnesota, but the Timberwolves' reserves outscored Denver's 48-17.
Jordan Poole scored 20 points and Jonathan Kuminga had 19 points for the Warriors, who lost for the fifth time in seven games.
On Wednesday, the Timberwolves announced that they have parted ways with Rosas just prior to the start of the 2021-22 NBA season.