Up until his disappearance in "End of the Beginning," Ozpin served as the headmaster of Beacon Academy.
Ozpin is the leader of a group whose goal is protecting the world from dangers that are kept secret from the public. Other members of the group include Glynda Goodwitch and Qrow Branwen, as well as the leaders of the other three academies - James Ironwood of Atlas Academy, Leonardo Lionheart of Haven Academy and the headmaster of Shade Academy.
Glynda is a fellow staff member at Beacon Academy. She is often seen alongside him when addressing students. Due to the blunt and honest manner in which she usually speaks to him, the two have known each other for a while. Their history includes both being a part of Ozpin's Group, a brotherhood dedicated to protecting Remnant.
Ozpin has known Qrow for years, as implied in Ruby's interrogation in "Ruby Rose". Ozpin was definitely present on Qrow's first day at Beacon Academy. In "Black and White", the two men are continuing an apparently-secret correspondence regarding someone code-named "The Queen".
When the two meet with Glynda and Ironwood in Ozpin's office, Qrow mentions that Ozpin invited Ironwood into the group's inner circle, implying that Qrow had Ozpin's trust far earlier. After Ozpin disappears, Qrow sees himself as the one to step up and take responsibility in Ozpin's place. This includes taking over Ozpin's Cane, which he later gives to Oscar Pine. This act indicates Qrow's awareness of more secrets about Ozpin than the show has revealed, particularly with the words "It's good to see you again, Oz."
It is revealed in "Rest and Resolutions" that Ozpin granted Qrow and Raven the ability to turn into birds to gather information and find out where the Maidens are. The two men seem to have a mutual level of trust, as Qrow quickly defends Ozpin from Yang's accusations.
Ozpin and Ironwood seem to be very good friends, speaking in manners unseen with most others. This indicates a rather personal level of familiarity. However, Ironwood's methods and views about security tend to clash with Ozpin's, resulting in the two being regularly at odds with one another. Though Ozpin considers the general misguided, he also notes that his heart is in the right place.
Ironwood comments that he has served under Ozpin for years as part of his secretive group; despite their differences, Ironwood still answers to Ozpin.
Lionheart was one of Ozpin's trusted lieutenants, but Ozpin starts to doubt him in "Welcome to Haven " after learning that he is not following several of his instructions. Sensing that something is wrong, Ozpin decides it is best not to let Lionheart know that Oscar Pine is his new reincarnation.
Ozpin seems to take a special interest in Ruby. When the two first meet, he is intrigued by her silver eyes, knowing about her linage, before commenting on her level of skill with her scythe, Crescent Rose. He also seems interested in Ruby's motivation for becoming a Huntress, in that she wants to help people. He is so impressed by Ruby that he allows her to skip two years at Signal Academy in order to enroll at Beacon Academy.
Even after her enrollment he continues to watch over her, completely ignoring Glynda's report during the Beacon Academy Initiation in order to watch Ruby's progress on his Scroll. He is also seen observing her in "Black and White".
During the year at Beacon, Ozpin appears at her side a number of times. After Weiss Schnee starts making Ruby question her appointment as team leader, Ruby asks Ozpin whether he made a mistake appointing her as team leader. The headmaster gives Ruby a pep talk, advising her that being a leader means acting her best so that she will be respected by her teammates. He then confides in her briefly, stating that he's "made more mistakes than any man, woman, and child on this planet" but believes his appointment of her as team leader is not one of them. At the Beacon Dance, he advises Ruby to enjoy herself, pointing out that fighting and dancing aren't very different.
He also covers up for Ruby, cutting off Glynda's question when Ruby tells him of a possible hideout in the southeast of Vale despite Ruby previously saying that Cinder did not say anything to her.
After Team RWBY is unable to get their mission in the southeast, Ozpin hints that he is aware that they have been up to extracurricular activities. He makes Ruby self-conscious and uncomfortable while listing unexplained events from "Black and White", "Extracurricular", and "Painting the Town", all while claiming he'll never find exact answers. Ruby's mood changes, however, when he volunteers to bend the rules for them to get their mission, since he suspects that they would make their way there anyway.
When Ozpin reunites with Ruby in "Unforeseen Complications", he apologizes to her and Team RNJR for the hardships they have gone through, despite Ruby saying that it is not his fault. To prepare her and her friends to fight Salem, Ozpin decides to train her in hand-to-hand combat.
In "Necessary Sacrifice", Ozpin describes Ruby as remarkable to Oscar. While he notes that she was the best Huntress at Beacon in some ways but not in many others, he remarks that she possesses a "spark" that inspires others even in the darkest of times.
The two are not shown interacting together during the Beacon Arc, though it's revealed in "Known by its Song" that Weiss knows of what she believes is his true past.
When they finally meet in "Rest and Resolutions", Weiss is startled by what Ozpin reveals to them, basically confirming what Raven told her and Yang earlier.
Ozpin is aware that Blake is a Faunus, and also seems to suspect Blake having some affiliation with the White Fang as he questions her on how she had known where the they would attack. In addition, he notes that she is one of only a few people who managed to enter Beacon Academy without the years of preparation to pass the rigorous entry exam.
He ends the questioning by offering her a listening ear, should she ever need to talk to him.
The two are not shown interacting together during the Beacon Arc.
When they finally meet in "Rest and Resolutions", Yang confronts him on turning her mother and uncle into birds. When she learns they chose and accepted the power, she relents. Yang agrees to keep fighting, on the condition that Ozpin not withhold any more pertinent information.
Despite Glynda's protests about Jaune, Ozpin decides to make him the leader of Team JNPR in "Players and Pieces", much to the boy's surprise. In "Unforeseen Complications", Ozpin decides to help Jaune in unlocking his Semblance. When Jaune laments about not finding his power in "Lighting the Fire", Ozpin tells him not to worry, as his journey is far from over and unlocking his Semblance will not be the end of it.
Ozpin has thought highly of Pyrrha since she began attending Beacon. He thinks of Pyrrha as strong, intelligent, caring and ready to be a guardian figure. In "Fall", Ozpin chooses Pyrrha to become the next Fall Maiden but allows her to accept or decline. In "Heroes and Monsters", Ozpin defends Pyrrha from Cinder and yells at her to get Glynda and Qrow to help him, not wanting her to risk her own life.
Ozpin and Salem are ancient enemies, the former being cursed to exist for thousands of years for failing to stop her. While Salem seems intent on destroying humanity, Ozpin holds a contrary view, placing both of them at odds with each other.
Cinder Fall is the main enemy of Ozpin and his group during the first three volumes. She successfully steals the Fall Maiden's powers that Ozpin's group tries to protect. They both meet face to face in "Heroes and Monsters" where she expresses her disdain for him and prepares to fight against him. In "End of the Beginning", both finally clash in the vault underneath Beacon, resulting in Ozpin's disappearance. Cinder later reports to Salem that she killed Ozpin, though Salem questioned her at least one more time as to the truth of this.
Ozpin informs Oscar in "Kuroyuri" that Hazel is a man from his past who is not to be taken lightly.
A fellow staff member at Beacon, Port shows a deep trust and admiration for Ozpin when defending him to Weiss, stating that he served under the headmaster for years; in all that time, Ozpin never led Port astray.
Ozpin first speaks to Oscar in "Family", but it is not until "Punished" that it is revealed the conversation takes place inside Oscar's mind. Ozpin informs Oscar that their Auras and souls are combined and Oscar's thoughts are now also his. Eventually Oscar comes to accept that they are one and the same, tentatively referring to Ozpin's Cane as "my cane" and telling RNJR that they know him as Professor Ozpin. Ozpin has taken to mentoring his latest incarnation, and in turn Oscar has picked up the habit of conversing with Ozpin during moments of self-doubt, relying on Oz's wisdom and experience when he is at a loss of what to do. By the time of "Necessary Sacrifice" Oscar has formed a mutual trust with Oz, consulting him on Ruby's nature as a person, forming a close personal bond with one another, and gaining solace in the battle against his fears of the upcoming war against Salem and her forces. According to Ozpin in "Unforeseen Complications", when he is reincarnated it is into a "like-minded soul" suggesting he and Oscar have similar ideals.