Normally when a movie is dubbed into other languages, a new voice cast is brought in. But because Groot in Gaurdians of the Galaxy is a Hodor-type character with, let’s say, a limited vocabulary, they just had Vin Diesel do all his own dubbing.
Here he is on The Tonight Show, being quizzed by Jimmy Fallon. I would like to program Vin growling in Mandarin into some sort of white noise machine, and have it infect my dreams from now until the end of time.
Marvel has also released a number of videos in different languages. Skip to the end of each to see Vin recording his line.