This is a very interesting question. On one hand, Bono can be judged as being non- interventionist and unwilling to involve himself to a certain extent in finding out about Rose and Troy. It is seen that he warns Bono about this in the First Act, telling him to disengage. In the Second Act, Bono displays his dissatisfaction by disengaging, himself, out of he relationship. This can be judged as being apathetic, to a certain extent. Bono can be judged as being someone who simply looks out for his own interest at a certain point.
However, I think that there is something deeper here. Both men are strikingly similar. Troy and Bono both befriended one another while in prison, both work at a job that challenges both in terms of discrimination and challenges, both men face racial challenges and hurdles due to economic limitations. Yet, both men approach their personal life entirely different. Troy is unable to find peace, or some type of psychological grounding. Bono is able to find some level of happiness. His relationship with Lucille is one where there is love, support, and the demonstration that a man can be faithful and happy. In this realm, Bono not only operates as Troy's emotional foil, but also displays how what it means to find happiness despite social challenges and difficulties. Bono speaks of "the walking blues" and tells Troy that such happiness is possible. Yet, when Troy consistently fails to heed Bono's advice about his relationship with Alberta, Bono might simply recognize the signs that both men are fundamentally different. Bono has struggled in the same way as Troy, and has fought to find his happiness. His disengagement might simply be his attempt to maintain his happiness while Troy is incapable of establishing his. In this light, Bono cannot be judged too harshly for not wanting to implicate himself further with the self destruction of Troy's behavior. To this extent, I do not think that too harsh of judgment can be rendered. Who among us has not had to leave someone who simply refuses to be helped? It might be here that Bono's character resides, as evidence of someone who can find happiness, who can find personal hope, and refuses to surrender that to anyone.