Rōshi

was the jinchūriki of the Four-Tailed Monkey. He hailed from Iwagakure. Another jinchūriki, named Han, who held the Five-Tailed Dolphin Horse, also originated from Iwagakure. It is logical to assume that he and Han knew each other, as they were both jinchūriki of the same village.

Background
Rōshi became the jinchūriki of the Four-Tails at a very young age. He left his hometown of Iwagakure at some point to better understand and control the power of the beast within him.

Appearance
Rōshi was shown wearing a large headpiece consisting of a three pointed crown-like ridge, bearing both his Iwagakure forehead protecter and ring, and a prominent black piece of armor running across his cheeks and the bridge of his nose.

Despite his advanced age, his hair was solid red. It should be noted that his hair and beard style were exactly the same as that of the Four-Tailed Monkey inside him.

Hunt for Uchiha arc
He was captured by Kisame Hoshigaki of Akatsuki, and later died as the result of having the Four-Tails extracted from his body.

Abilities
By borrowing the Four-Tails' power, Rōshi was able to use its Lava Release ninjutsu, a combination of Fire and Earth-based chakra. He was also shown with a unique, curved kunai. Kisame Hoshigaki, when talking about his fight with Rōshi, mentioned that Rōshi was capable of many recomposed Nature Transformations that are rarely seen outside of a Kekkei Genkai, hinting that at least the Lava Release style may not have been the only trick in Rōshi's repertoire.

Trivia

 * means "old age" or "elderly". means "purple". It is possible Rōshi was named after the Dragon Ball character master Rōshi, considering that the Four-Tails' design was also inspired by Dragon Ball.