Rossi, a nine-times world champion across all categories with seven titles in the top class, has not won a race since 2017 and split with former crew chief Silvano Galbusera ahead of the 2020 season with Munoz stepping up from Moto2.
Munoz helped Francesco Bagnaia clinch the Moto2 title in 2018 and Rossi said the Spaniard's personality was exactly what he needed at this stage of his career.
"Last summer I understood we needed something different. We changed the mechanic and bet on a mechanic from Moto 2," Rossi told reporters at a virtual news conference ahead of the Czech Republic Grand Prix weekend.
"I feel very good, he can teach me a lot. He's very different... He has a lot of experience with the settings and the chassis.
"Apart from his technical skills, his approach is very quiet and optimistic. At this stage of a rider's career, this type of support is important."
Having gone without a top three finish for more than a year, Rossi finally returned to the podium at the Andalusian Grand Prix last month in Jerez after he and Munoz convinced Yamaha's mechanics to change the settings for the Italian's bike.
The podium was the 199th of Rossi's premier class career and he has the chance to extend his record to 200 in Brno but the 41-year-old said the milestone did not matter to him.
"I'm not here for the 200th podium," Rossi added. "I'm here because I like to race motorcycles.
"It's just a number in the end. When you're old, you see the numbers and you're proud but it's not a motivation for me to race." (Reporting by Rohith Nair in Bengaluru Editing by Christian Radnedge)