Roy Batty and Deckard are both able to show us what it means to be human.
Through Blade Runner, we see an epic quest filled with meaning and symbolism applicable to the human condition. Replicants are basically human beings, except for the fact that they lack a history. As a consequence of this, perhaps, they also lack proper emotional faculties especially empathy. Empathy is the ability to place oneself in the position of another living being and understand that person's feelings. .
Blade runner promotes that empathy is the defining characteristics for humanity. The replicants, designed not to show any emotion, develop spiritually and emotionally throughout the film. .
The characters in the movie, even the ones that were not human, had many humanistic and believable qualities. Many of them were able to feel love as well as hate. .
Although Deckard is supposedly human he at times shows less emotion than Roy. He seems heartless and uncompassionate making himself look very unhuman. We see that Deckard is possibly not "human" as well, but a replicant. He shows no compassion when he tells Rachel of her being a replicant with implants. In tears, Rachel sneaks out of Deckard's apartment and into the streets. The only time in which Deckard really shows emotion is accomplished when Roy, forging Deckard through the fires of a harrowing battle, looks terrified knowing that he is going to die. Through this, Roy tries to communicate his life experiences, and the importance of life before his own flame extinguishes explaining of the horrors of their enslavement. .
Again, all of these human characteristics that the non-human characters showed makes them more believable for the viewers. The whole definition of humanity is changed by its interaction with the Replicants. .
For the replicant Roy Batty it was obvious that that he felt strong emotions, perhaps even love for his fellow replicants. After Deckard killed Pris, Roy leaned over her and kissed her showing that he had loved her.