So I mean this in a sort of general term. In the first entry of Rorschach's journal at the beginning of Watchmen, he pretty much just gives a monologue about how he hates humanity in its current state and can't wait to watch the sinners die. I get that Rorschach is a detective and in a flash back we see he avenged a little girl who was kidnapped and killed, but he is supposed to be a hero isn't he? Hollis Mason says to Daniel that Rorschach is the only one still on the streets but we never really see him save anyone. The furthest he goes to protecting people is warning Daniel that someone might be "hunting masks" so did Rorschach ever help people? And if he did was he still doing it at the beginning of the movie?
We're given a few clues about what Rorschach is up to at the start of the movie before he gets involved in the detective work and 'old boys networking' required to investigate and propagate his 'mask killer' hypothesis.
Rorschach has clearly continued his crime-fighting activities despite Nixon's attempt to make them illegal. He's bitter that he has to do this on his own as evidenced by his negative comments about Daniel's flabbiness and the perceived 'failures' of those Watchmen who have ended up murdered or in mental asylums.
There's an off hand reference to his being on the top 10 Most Wanted list for his activities and the policemen who eventually bring him in clearly have no sympathy for his activities. Even the reaction to his appearance in a low life bar is enough to show that he is still perceived as a brutal, vigilante enforcer in the criminal community. You're right that we never see him save anybody but it is strongly implied that Rorschach had always preferred harsh retribution to rescue missions.
In addition he has his other life as a down and out on the streets. We see him unmasked in various scenes in the movie toting an apocalyptic sandwich board and observing his former colleagues.
It doesn't seem like a very fulfilling life but given Rorschach's character, background and unremitting fervour this is unsurprising.
Rorschach is a vigilante. He is dispensing his own form of justice, saving a society that doesn't DESERVE to be saved. But he does it anyway. You could argue, as some do in the comments, that by killing the worst of the unworthy, he is making life more tolerable for the rest of the unworthy (in his eyes). It jives with his moral code to do so, when his first inclination is to let all of society kill itself.
He was still doing it at the beginning of the movie (and the novel), but at the moment he was focused on solving Comedian's murder, which he of course he did solve. Is he a detective? Only if you would still consider Dirty Harry a detective if he gave up all pretense of arresting the criminals and just shot ALL of them, instead of just some of them.