is bernger's last speech heroic or not in rhinoceros

I think you'll have to make that decision based upon your reading, but here is gradesaver's take;

Left alone on stage, the only remaining human in the world, Berenger delivers a powerful monologue. He begins with heartbreak at Daisy's exit. He is certain that "I'm staying as I am." But he loses sense of reality, asking existential questions such as, "What is my language? Am I talking French?" and "What do I look like? What?" He then, for the very first time in the play, sees beauty in the rhinoceroses. "Oh how I wish I looked like them... Their song is charming." He even tries to turn into a rhinoceros by making their trumpeting sounds and asking for a horn to grow—but he remains human. Then, suddenly, he snaps out of it. In the final lines of the play, Berenger declares that he will "put up a fight against the lot of them. I'm the last man left, and I'm staying that way until the end. I'm not capitulating!"

Berenger’s final monologue proudly affirms the character's individuality and commitment to a moral code. As he declares his individuality and his resolve to fight, we hear the playwright's message most clearly. We are to focus on Berenger and approve of his resistance. We feel the call to engage politically and personally in society so that people do not become rhinos or get taken in by banality and false reasoning. If we do not take this responsibility, Ionesco warns, we easily will become dangerous, unintelligent animals.

At the same time, however, we now must confront the meaninglessness of everyday life. If everyday conversation is banal and illogical, and if efforts to understand and live well in the world end up in loneliness and absurdity, what is the thinking man of resistance supposed to do with himself every day? At the close of Act I, Berenger took another drink after talking to his friend about how he wanted to stop drinking. His point of view lacked hope, and he could not find a redeeming value in everyday, ordinary actions. At the close of the final act, Berenger emerges a strong, resilient fighter, a defender of his humanity and, indeed, the human race itself. He has something noble to do. In this heroic character transformation, Berenger answers the philosophical question that once plagued him. In order to find worth in his actions, it seems, one must believe in a cause and fight for it.